I'm 6'5", which means that dunking a basketball isn't all that impressive. Other relevant stats on this front: I weigh 190# and squat nearly 300#

My height also means that I ride large frames. This Raleigh is a 60cm, with 59cm top tube (albeit with very short wheelbase). But my other steel bikes are larger (63-65 cm), with longer chainstays, and I'm not getting brake rub frame flex when sprinting on any of them.

I'm going to touch up the tension on the wheel but I assume it's all okay. I'll check again for cracks in the frame, but I'll probably just loosen the brake cable slightly and not sprint too much on the bike.

P.S. the brake cable or housing isn't a causal issue here, although certainly was worth mentioning.