Okay, I have to amend what I said earlier about my experiences on finasteride. First of all, I did acquire more body hair while I was on finasteride, and my voice did go from a tenor to a baritone, and my sex drive was pretty much unchanged.
But I was off it for a few months and then went back on it. Short after I restarted it, I realized that I had had a lot more hair growth in the past few months while I was not taking it. My mustache got darker and just a bit coarser, but that will take time. The hair on my belly started creeping a little higher, up toward my chest. I started getting hair higher up on my thighs. I'm getting hair on the backs of my upper arms (lots of growth, suddenly), as well as back hair, which I've never wanted. But I'll deal with it.
And...I was getting significant chest hair growth.
I really want the body hair, but I don't want to lose more head hair. So I'm kicking myself. If I'd started transition a few years earlier, I might have gotten a bunch of body hair without having to sacrifice head hair, and so I could start finasteride without reservations. Now I feel as if I have to choose between body hair and head hair!
This could be good news for you. You have said repeatedly that you want to keep your head hair but not get body hair. Obviously, YMMV, but I thought I would put this out there. Just some food for thought.