It's the contrary - you generally first lose the weight you last gained. So, for example, someone having always had a lot of fat in the butt and waist, then gaining a belly over a few months, will first lose the belly. But that's just a "saying" I hear from family members and the TV. It may not be all that true.
As for your question... Well, in a worry of utmost safety, I think it's probably best to stop losing weight until fat has stopped moving, in about 2-5 years, given that with your height, your current weight is just above in the healthy area... But it feels sort of silly to stall your weight for such a long time, doesn't it?
This is all zero-expert theory, but since fat doesn't "move", but is rather gradually burned in a higher priority in male spots, and put on in priority in female spots... Perhaps it would be a good way to go to try some sort of roller coaster weight loss regimen, as in losing 3 pounds, then gaining 2, than losing 3 more... But then again the instability might stunt development.
There's also this: since it usually takes 1-3 months, I think, to get your hormones to female levels (could be faster since you started spiro before though). Your serum levels of oestrogen are probably still low, which would mean that fat redistribution hasn't really started yet, and won't for a little while. And it really, really comes gradually. So it's probably safe to assume that if you do some kind of blitz to lose the rest quickly, fat redistribution will really start after you're done, which would probably be equivalent to you having lost it all before HRT.
But keep in mind that, as far as I know, at least, there is still no hard evidence (or research for that matter) that weight loss really has an influence on feminisation, and if it does, whether there is a "safe limit". So you'll never get a certain answer. But even though it's close to impossible to determine whether a person has achieved optimal results or not, there have been transitioners who lost weight during transition and who ended up fine. So whatever effect there can be is probably no so devastating!
PS: Congratulations on getting HRT so soon! I started when I was about your age, and only just managed to get on HRT this February. Have a little shot of envy flame thrower.
