All I have been able to dig up is a lot on Mr Maki the architect and the fact that
"Maki's gym is restrained and sober, a mature fantasy. The flawless, parabolic stainless-steel skin is 1.6 acres in size but just about one-sixtieth of an inch thick".
Now 1.6 acres is an impressive roof! For morefrom where I found the above:
http://www.time.com/time/magazine/article/0,9171,965570-3,00.html copy
Googling the full word 'Gymnasium' spelled out rather than just 'Gym' (ie Fujisawa Municipal Gymnasium) does pull up a lot of images and websites that might contain the height dimension - but I have to go out so I can't plough on. Best of luck. I'm sure someone else can find out.