Your theory is irrelevant, in my view, where it does not offer a solution to the problem of sustainability in relationships. You insist that this is achieved through incorporating yoga in the routine, but I disagree that it needs even consideration at this stage of the commitment of two bhaktas. Body is not the first priority in our tradition.Let me say that I think that this sādhana is at least potentially a solution to the sustainability of relationships. Prema Prayojan Dasji's model of sādhana in a couple, i.e. where the husband and wife participate as companions in bhajan of Radha and Krishna, is pretty much right on.
But I certainly don't think that any relationship can be sustainable if there is not a third point to the triangle, which is the Sacred, which in our case as Vaishnavas means Radha and Krishna. Without that external focus of the Divine Ideal, how can there be sustainability? Even the Catholics say the family that prays together stays together.
But the concept I am trying to present is direct, in that it focuses the mind of the sādhana partners on Radha and Krishna in the state of purest love. In other words, the sādhaka partners focus the mind together, i.e., simultaneously, in śravaṇa, kīrtana and smaraṇa, the three primary practices of bhakti. In my opinion, this culture should be done in seclusion and not simultaneously as members of a crowd.
Just as an individual should practise seclusion and learn to meditate and chant, etc., at least part of each day by him or herself, in order to quieten the mind, so should the bhajan of the couple be done in seclusion. The capacity to do bhajan in individual solitude should be considered a necessary PRE-requisite to attempting Yugal Bhajan. Doing Yugal Bhajan without a solid grounding in individual sādhana -- over and above community practices -- is an impossibility. This is why we make a distinction between the pravartaka and sādhaka stages, the singular and the dual.
By the same token, without the kind of sexual and psychological stability, harmony -- and indeed love -- that comes from the combined energies of a loving man and woman who are cultivating bhakti-sādhana together, I think that preaching activities will fail on the level of community aspect, at least where sustainable communities are the goal.
And it goes without saying that they are, if Krishna consciousness in any form is to thrive.
With regards to yoga. Even before I went to Rishikesh, I had incorporated many kinds of yoga practice, most particularly since I had been a babaji in Nabadwip when I was chanting one or more lakhs every day. I gradually changed my way of doing things so that I could sit more solidly and improve my japa and smaraṇa. So this is not something that I have just added recently. But I will admit that staying in Rishikesh gave me a lot of opportunity to improve my understanding of much of yoga theory and mechanics, which has really been very good for me personally.
Since smaraṇa is the pran or life of bhajan, it would seem to me that anything that is favorable to smaraṇa would be favorable to Krishna bhakti and Radha dasya.
Sorry this is getting long, but I would like to add a little more, since I think the yoga question may have something to do with the elements of seminal retention or orgasmic control. Some people may find this a bit too esoteric, but I consider it just the normal way of establishing control over the sexual machinery in the body. This makes both "separation" and "union" untroubled by physical lust. Because this aspect of spiritual practice is not generally discussed in orthodox circles, who restrict themselves to directly bhakti (svarūpa-siddha) practices, we call it deha-sādhana. But let this not be a source of confusion.
All yoga methods, including bhakti, begin from the external and move to the internal, from the most gross level of the body and then to the mind, śarīram ādyaṁ khalu dharma-sādhanam. Certainly the Gita does start with the body. Its first six chapters describe a gradual spiritual culture that proceeds from the gross to the subtle. There Krishna first tells us that we are not the body so at least we preliminarily get the proper orientation, the sambandha. But no one is expected to "get it" right away and therefore there is a necessity for sādhana, the abhidheya. Then at the beginning of the sixth chapter (6.3), Krishna makes it clear that we have to proceed from mastering the body to mastering the mind, and from there to awareness of the Self and God.
Bhakti is also the same. Vaidhī bhakti is predominantly about external sādhanas, rāgānuga is manaḥ-pradhāna. That is why there is a little bit of disagreement about the necessity for vaidhī bhakti as a prerequisite for rāgānuga. So a mixed sādhana is recommended for even those who wish to attempt even rāgānuga. But one of Rupa Goswami's basic definitions of bhakti is that it is "serving the master of the senses through using the senses," hṛṣīkeṇa hṛṣīkeśa-sevanam. The senses include the mind, which is the eleventh sense. But the inner aspect of bhakti is feeling (sādhya-bhāvāḥ), not just awareness. (BRS 1.2.2)
The sexual element in the Yugala-sādhana is nothing more than an attempt to engage this particular sense in a way that is beneficial (anukūla) to the goals of bhakti. This is actually a most brilliant discovery. When a devotee sādhaka and sādhikā, whose attraction to one another is primarily based in their shared interest in Radha Krishna, whose love for one another is based in recognizing the love they each have for the Divine Couple, who are committed to helping each other purify themselves in an honest attempt to become free from their personal psychological obstacles or anarthas, engage in the act of lovemaking, there cannot be anything that is detrimental (pratikūla) to bhajan.
I recommend chanting the name of Radha and Krishna while making love so that the pleasurable experience of such sādhakas' union, the most intimate sādhu-saṅga, who pour the love of their soul for the Divine Couple into their union, doing śravaṇa-kīrtana of the Holy Name while in the ecstasy of this most intimate union will make smaraṇa of the Divine Couple a real and living fact of life. Who would wish to give up this kind of intense spiritual intimacy (sādhu-saṅga)?
I really cannot understand why anyone would have an objection.