Well past that. Again, we're talking a fraction of a percent of the total population. Letting trans women compete with cis women means you'll see the occasional trans woman competing, and occasionally dominating the sport.
Just to put this into perspective a bit, there are about half a million student athletes each year, and close to that number of trans people across all age groups in the entire US. Trans women dominating sports at any level just isn't something anyone should be worried about.
Estimates I've seen put the trans percentage around 1% in younger generations.
What I'm digging for here is at what % people think we would see a negative effect on athletic participation from AFAB individuals (or you could of course argue for why we wouldn't see such a decrease no matter the %, but that doesn't sound realistic - giving kids role models they can relate to is important). Because that is the negative consequence that gives me serious pause, not the personal lives of a handful of athletes that either would or wouldn't be competing at those top levels.