Have you tried gaining your own weight first and seeing where it ends up?
Since you're already on HRT and you're very thin any new weight
should deposit into feminine areas.
What I would do is for a few weeks track your calories at myfitnesspal and eat 500-1,000 more than your total energy expenditure (you can calculate it here:
http://www.health-calc.com/diet/energy-expenditure-advanced).
If you eat 500 calories more per day than you burn you will gain about 1 pound a week. If you take measurements of your body before and after (these can also be tracked at myfitnesspal) then you can see pretty much exactly where the new weight is going.
And if you don't like the results just do the opposite to lose the weight again by eating 500-1000 fewer calories than your TEE.
