About 5 or so years ago both Dman and I ran all the flavors of Thrasher including the "108" at about 25 lbs (93 octane) w/no real problems to mention. That was totally stock, you know, stock IC / turbo / injectors / heads, etc.
I do remember some knock in OD. I think it started to spike. Sorry, memory not great and too dang lazy to dig out the DS data.
I'd guess, judging from other high-timing chips I've used, the T-108 timing is likely 28 degrees or so.