Should I be trying to gain weight before starting hormones ?
I know YMMV, is their a correlation between body fat % pree ht, and breast development?

I wouldn't gain any weight.  Once I was on HRT, my weight started to go up and it is very hard for me to drop weight.  On breast size, they say look at your female relatives.  You will probably be somewhere around their size.

Good Luck,

Julie