Now I'll get my flame suit on by suggesting that all this talk about frame stiffness is a red herring when one fails to consider the load being offset on a rack connected by four flimsy attachment points, particularly the two near the top of the seat stays.Those are far more likely to wag the dog when standing and throwing the bike back and forth to crank than the frame itself.

wanna see now much? Just secure the front tire to the downtube, stand the bike up, grab the back of the rack and throw the bike back and forth. If the rack flexs that is what will throw you off when standing and torquing side to side with a load on.

plus yes... you just have to get used to it. No heavily loaded tour bike is going to handle like an unloaded road bike.

Low gears are good for going up hills. Standing and cranking has its place for stretching, butt breaks and air flow but if you want to tour loaded it's far better to use gearing as the default technique. I've never heard anyone complain about having a low granny gear bit have heard some about not having one.