I never go past 315 on the squat if I were to go heavy and that is rare boxing and thai boxing...if I do I don't spar for a day or so after b/c my legs feel heavy as hell afterwards.
after jogging miles, jumping ropes, polys, high reps low weights, sparring, bag work..etc,etc....you simply don't have the leg strength to go heavy imo. If you do...then next day or so you need to limit movement because your legs won't be there imo