I too am large like you. Maybe you need to adjust the brake/clutch levers down so that your hands aren't bent backwards all the time. That seemed to help me a little. Also, I had to focus on always squeezing the tank with my knees and putting my feet farther back on the pegs which helped to keep my body weight off of my arms. In the end, I'll have to find a throttlemeister or equivalent so that I can relax both of my arms instead of just the left. I may even start wearing a wrist brace on my right wrist. To help keep my long back straight, I am thinking of ordering a 'back-a-line' type of kidney belt.
My wife is probably right when she says I need to exercise and lose about 20 lbs.
Hope this helps.