I suppose I should chime in too..
Interesting, and fun thread..
I have never experienced any shrinkage, though the thought and desire would/and is appealing.
PM has really changed my need for sex. It's less 'penis' focused. I've noticed other areas of my body more sexually stimulated - nipples and anal, by far is more pleasurable. I suppose that's the flowing nature between my male and female side, but I am more in tune with my body and it's really re-enforced/and validated my femme identity. Sex as a 'male' doesn't interest me, and frankly, hasn't for years, even before NBE.
I can still get erections. They're tough to get and maintain, but it doesn't bother me. Nothing spontaneous anymore.