Very interesting discovery with removing the weight from the end of the bars...and when you think about arm X moment it makes sense.
I am one of those kind of riders that sort of adjusts to the bikes idiosyncrasies, and although I notice the effects, I look at it as my getting used to being on the bike after a long winter. After a while, my muscles or something builds the strength at certain locations, and I find it never really bothers me again.
Several years ago, my riding buddies had our first ride of the season the first week of April. We rode about 100 miles and stopped at a lake resort...whereby the fatigue was insane. We rode home and my friend on his BMW K1200Gt could barely climb off his bike, he was that twisted/sore/fatigued that I started thinking we were getting WAY too old for this recreation. In October, we went on a 450 mile ride for the day, and I distinctly remember both of us not having a problem at all with the ride. Strangely strange, huh?
Anyway, I may experiment sometime this summer with removing the handlebar weights, and get a good feel for any improvement. If so, I will get some lightweight aluminum end caps to put in place. Thanks for the post!