Yes, Smith Basses are heavy, that why I bought one of these-
http://www.comfortstrapp.com/
THE BEST strap I have ever used. Relieved my shoulder pain completely even on 4 hour gigs, however my back pain remains. No strap will relieve an aching back from that hanging weight. I get a burning sensation across the middle of my back, just below my shoulder blades. The heavier the bass, the worse it gets.
Heavy doesn't always mean good tone, tho. I recently had a very hi-end bass made for me that was in the 12lb. range. The body was 5A flame maple with Asian ebony on top. BEAUTIFUL- but the tone was, well.., blah. I even tried different p-ups. Just couldn't wake that thing up. So now it's gone, and I'm going back to Smith. My 1st Smith bass was just a simple BSR5M-A, ash body, and I've owned 3 other Smith 5's since, and it was probably the most responsive of them. And it was a light-weight. Wish I could get her back....
Chris