Flipping logs is pretty cool, it is different from a tire because once you clean it you still have to press it and walk it over. Adds a new element to the movement. Oh, and I'm guessing you would be fine with a 400-500lb tire. I don't know anyone that can't flip those. I have two 500lb tires at my house (a single 500, and two 250's bolted together) and they are really pretty easy. I can run a 100' course flipping in under a minute at this point. The other weekend I flipped one for 50 flips. Took me a while, but that wasn't a ton of rest between flips.

Once you have the technique down it really doesn't take much energy to flip a 500lb tire. We don't have a lot of big earth mover tires around here, since we are a farming community, but tractor tires are all over the place. The clean on a tire is much higher, but on those tires you guys have you literally just walk them up.