Hi Simon,
I have commented in a few places before. Being too lazy to go look for those, I’ll duplicate a bit here. 
This is a song I very much wanted to play. It has the groove and simplicity I enjoy. And, I seem to really like shuffles… In hindsight, that would have been a good avatar name for the forum!
I can say that playing on the SG vs a longer scale S-style does make a little difference while you are getting your hand to make the stretch. I can kind of make the longer scale now, and the shorter scale is pretty comfortable and sounds clean.
If you want to play this, work on the stretch daily for several weeks. Don’t be impatient and try to force the stretch. Extend your fingers as much as you can and hold it until you feel a little fatigue, then release and wait a few moments to let your hand rest, then repeat. Do this 10-15 times, then let it rest by doing something else. Repeat this morning and evening and it won’t take long before you notice you can reach further.
I would massage my hand throughout the day. Eventually, this wasn’t needed. I could feel it getting tight and also feel things pop. There are a lot of connective tissues in there that all need to adjust to making a new motion. This can take a few months, so be patient.