Here's an idea that I haven't seen around here.
I had these on my Buell XB12S and they worked really well.
http://www.throttlemeister.com/
It will work with pre TBW type setups like yours.
The end weights themselves help with the dead arms anyway.
The weight at the very end of the bar makes a big difference in felt vibration when you ride any distance.
You just curl your pinky finger around the end and turn it back slightly , this engages the friction.
They never get tight enough to lock the throttle from a quick decell if you need to.
My brother uses this setup with a cramp buster http://www.crampbuster.com/ and it really helps with his hands also.
I run Kuryakyn ISO grips which have the throttle boss , and this helps a little anyway.
Mick