Rain
kennywtelejazz
Yeah , it's a real cool guitar . I saw one up close ( the original model ) back in 1980 and have wanted one ever since .
talk about shoulders and pain ….
oh man , it's your right shoulder for you …and it's my left shoulder for me ..
my left arm is all metal from the ball ( absolute top of my arm ) to a couple of inches above the elbow ..
Kenny knows shoulder pain 
Then you have it much worst than me. :/
I probably have an issue with the rotator and/or with a nerve. Everything between the side of my neck to the tip of my finger is either painful or a tiny bit numb. So it's a matter of position - most guitars require me to lift up my elbow a bit more and to push it forward a bit, which results in pain after a few minutes.
Playing bass is the worst, because the bridge is much farther down, close to the edge of the body. My Riviera is also quite uncomfortable.
But the SG is so tiny that my arm is in a completely relaxed and natural position. I can play it for hours w/o any problem.
So I decided that I needed a SG w/ a Bigsby and a pair or TV Jones. :P
More seriously, I've recently discovered a thing called ice packs, as well as joint rubs. My father would probably call me a wuss, but, it's surprising how a little care can go a long way in healing a wound.:)
Rain , I hear you on having to adjust your physical position to be able to play guitar as pain free as possible
I spent my whole life playing the guitar placed on my left leg in sort of a classical seated position when I play sitting down
everything changed after the accident (4 years ago) ...I couldn't even play or hold a guitar for the first year
Now I enjoy playing more than I ever did , probably since I know that I got a second chance at it ...
I still have a few range of motion issues with every guitar that I own if it put it on my left leg as in my former playing position …
standing up playing with a strap I'm much more comfortable w the solid bodies , not so with the full sized Jazz boxes ..
I have an Epiphone limited edition 61 reissue w 2 P 90's in Alpine White …I love that axe …very comfortable to play
Yeah , since your body is trying to tell you that it don't hurt when you play your SG ..that info may warrant further investigation
when you get the coin maybe you should get an SG w the TV Jones Pick Ups and Bigsby
here's what I play when I want that type of configuration and sound
nice rapping w you ,
Kenny