OK.. Just deleted my post, so here it goes again.....
As a MTF who did 41 years of boy mode, here is my observations on shaving/trimming.
1. Lots of guys shave their back. Most people don't "dig" back hair!
2. Some guys shave their chest/stomach. Its kinda out of style to have a hairy chest like Tom Shellac(SP).
3. Most guys will trim nose hairs, "uni brow's", and facial hair like beards/mustaches. Looking like "snaggle puss" isn't cool!
4. Some guys will trim their privates..... It helps in the "BJ" department, since almost nobody likes playing "kissy face" with parts surrounded with too much hair.
5. Most guys don't shave their armpits, unless they fall into one of the below mentioned groups.
Guys that shave/trim in odd places:
Hard core cyclists, swimmers, body builders, porn stars, "wanna be porn stars", and male models.
If you want to groom yourself in a "typical" male sense(IE to pass more) then keep it to the list above. I'm not saying you can't trim down below or your arm pits, but its kinda like a MTF deciding that having hair legs is gonna make them "pass" better than shaved legs. Now if your not worried about passing/blending in, then disregard everything I just wrote. But I suspect you will find shaving odd locations will "clock" you like a five o'clock shadow clocks a MTF.
Hope that helps! I have this really strong urge to help you guys in any way I can. I guess its kinda like..... I'm a failure at being who I am(Female), so I suppose I feel kinda "less worthless" helping you guys. If I am?

Dani