I haven't looked at your stuff (and don't really want to xD), but I'd tend to say that maybe the total foreskin stuff is a bit larger than the actual length. Ya know, if you pull a little. There's that. Also, I'm not completely sure how, but I think depth can generally be a bit more than the original thingie's length. And well, I don't think even the smallest thingie can render SRS impossible. The worst you can have is not much depth. And since, the way I understand it, you intend to be with your wife, that shouldn't pose much of a problem under those circumstances.
Now if depth is a concern to you, it's always possible to use a skin graft (I think it's from the inside of the thigh) to add quite a bit of material. That probably isn't just as sensitive as just your genital skin, but I can't say. I do know though that results can be more than acceptable. It does leave an additional scar, but I'm pretty sure that's something that can eventually be taken care of, too, in the same surgeon's office.
As for testes... Yes, they shrink from HRT. A good 50 % at least, and for me at least, it happened fast. But that isn't necessarily an issue for SRS. The scrotum shrinks gradually because the stuff inside is smaller, yes. But the same way the vagina's size is maintained through dilation, you can prevent shrinkage with just pulling on the bag regularly. And even if you don't, seriously, I don't think the loss is that terrible.
And the penis... it does shrink, but nowhere as much as the testes. 25 % maybe? But the way I see it, that thing is designed to have loose skin around anyway, so there's room for erections. So technically, a shrinkage of the organ inside shouldn't make the skin shrink so much, right? And even then, probably the pulling method works here, too.
