I'd look for a buck that's closer to fancy's size but that's just me, You can definitely breed her to a smaller buck like a nigie, i just wouldn't go with a buck that looks stunted small.. I'm not too sure about looking at his testicles, I myself wouldn't know what to look for there. But yes, I'd make sure he's proportionate. I'd look for things like a strong topline, good length and body capacity, no leg problems. You want to breed her with a buck that looks nice and strong and wont fall apart as he ages. If you do go out to take a look at the bucks try taking pictures of them and maybe I can help you out? I'll have to pop over on your thread and take a look at Fancy again.. I only remember her from when you first got her~ How old will she be when you plan to breed her?