I used to be in the "too small" camp regarding .224 cal centerfires on deer, but with the fairly recent introduction of true big game bullets in .224", I'm not so sure anymore. In fact, I'm curious enough that I might just try poking a 55 grain Barnes TSX through a deer just to see how fast it really dies, probably from a .22-250 Rem. .224 cal CF's are legal in the rifle parts of MN, so maybe if I go up there next year I'll take one along and find out for myself.
Mike