Andy, I have no doubt you have seen the 80 gr. bullets work. So have I.
I have seen around 25 deer killed with a .243 with one sort of bullet or another, and probably half of those were with what I would call "unsuitable bullets for deer". A group of guys I hunted with for a few years all used .243's and wouldn't listen to me either.
They thought velocity killed things.
I currently load for two .243 rifles for my son (although he's 32) and a friend.
Of those 25 I have seen only two cases where the .243 might have been called not enough gun. In both cases I believe the fault was not the cartridge, but the varmint style bullet that caused all the problems. I have never seen any problem whatsoever with the .243 on deer when used with heavier bullets.
So, respectfully, I always recommend 100 grain bullets in the .243 for deer. I think the lighter ones are not good deer bullets.
One not inexperienced man's opinion. I hope that's OK. No personal attacks are intended at all.