Any thoughts on running a .300 WSM with a 1 in 8" twist for shooting heavy bullets? Yes, I'm sure a 1 in 10" would be more than adequate, and there would be spin drift, but what are the actual pros/cons of using the faster twist?

Bullets can blow up due to higher centrifugal forces, possibly higher pressure with lower velocity...

+1 on Ammoloader's post. Add spin drift and it will magnify dynamic instability in bullets that tend to exhibit that characteristic like 168gr SMK near transonic (something I have noticed shooting M852 out of 1-11 guns past 600-700m).

If a 1-10 will adequately stabilize bullts a 1-8 will not make them more stable. I have shot 220gr SMKs out of a .300WM in a 1-10 with good performance to past 1K meters in the Mk248 Mod1 load.