I think your heading in the right direction ... I agree on lace vs. skin since you are a gym professional ... I'm thinking you won't like skin as much because of sweat, hygiene, discomfort, etc.

Have you looked into iLace at all? My understanding is that it's 2 layers of Lace, w/ hair knotted to the bottom layer and pulled through the top layer ... so you can't see knots, looks more like injected skin w/ hair "coming right out of the scalp," and it would be more durable and should be able to easily support 70% + densities (although regular lace "should" be doable at this density too ...)

I should add that I'm currently with one of the big chain "clubs" and in the process of switching over to DIY with online/mail order purveyors. On my head right now is an all lace piece (probably more like the more durable French style, but I'm not sure) and it is still TOO dense for me ... in my forties with kind of thin texture and density ... so I KNOW from experience that you can have lace w/ pretty thick density.