Not wanting to derail this thread (it's a good subject), I'll reply to the OP now I'm here...
In my opinion, there is no perfect solution to the problem. I'm no expert in physiology but it seems pretty clear that trans females have a distinct advantage over cis females in any sport based on speed, strength, etc. I think studies have shown that simply reducing testosterone levels to those of a cis female does not negate all the benefits that going through male puberty grants.
On that basis, I don't really think there is any fair option other than for them to be banned from female competitive sports, unless it can be proven that they have lost ALL benefit of growing up male, through hormone therapy. If that takes five years or ten, then that's just hard luck, imo. The way things are going with women's records being broken by people who grew up male definitely needs to be reviewed, imo.
I have seen some people say there should be new categories (trans F to M and trans M to F) but, realisticaly, there will never be enough competitiors in those categories to make it viable / entertaining. Which means trans people just need to accept that a consequence of transitioning is that they probably won't be able to compete as professional athletes.
It's a little harsh on trans athletes, but 99% of the population aren't able to become elite athletes... Just get another job like the rest of us, I guess?