Here are my thoughts....
IG Speed 300 (57)
IG Rad Pro (57)
Exo Tour 100 16 x 18 (54)
Those 3 frames all play with some nice flex. The Rad Pro is just an amazing frame for those who can handle the massive SW.
Yonex Ezone Ai98 - Yonex Poly Tour Pro (Black) @ 51/48