I didn't know you hadn't run deca. Most find it makes their joints feel good. Regarding the buildup of progesterone - I'm not at all convinced of this. 19-nortestosterone is a progestin, which means it attaches to the progesterone receptor, not that it promotes progesterone. My understanding of so-called 19-nor induced gyno is that it is very much a feature of estrogen-primed tissue. In post-partum women, progesterone drops suddenly. In the presence of estrogen-primed tissue, this signals the onset of lactation. If 19-nor doesn't act as strongly on the progesterone receptor as actual progesterone, what may happen is that the body notes a brief rise in progesterone-receptor activation (as 19-nor attaches to the sites) and then a perceived drop in progesterone, because the receptors are busy dealing with the 19-nor. 19-nortestosterone doesn't have as strong of an afinity to the progesterone receptor as progesterone, so if it is not as active, the body could indeed perceive this as a drop in progesterone.
A man on a cycle has a lot more testosterone in his body, and hence, more aromatase. This will be amplified if he's carrying any excess bodyfat. Toss nandrolone into the mix at this point, and estrogen-primed tissue meets a perceived rise, then drop in progesterone - and knows exactly what's going on: you're having a baby! Voila, lactation.
Perhaps run a mild SERM before you start on it. Does stanozolol act in this capacity?