After 3 years of passionately playing my fender jazz bass, my left shoulder has given out (shooting pains down my arm and across my neck). It's obviously too heavy for 4-hour gigs (and my 128 lb female body). Any suggestions? Any one know of a lighter-weight bass with a similar sound? A certain type of shoulder strap that provides more support? Weight-lifting exercises? I tried sitting down at a gig last night but those sultry blues just didn't have the same effect from a stool.