High Comp Hedas, Detonation and crummy fuel?

[Chazmanian]

I couldnt quite get a good grasp on what I was after via the search function so here goes....

8000-12,000 feet mountain riding.

800R with an HPS Can and an RKT head with 14.6 domes.

Crummy Colorado Ethanolated 91 gas

450 Main jets with shims.

Safe and all good on straight Ethanolated pump gas? Or detonating beast?

Anyone on this combo riding at 8000-12,000 with issues? Is 14.6 too much for 91 ethanol gas at 8000 on the trail heading to the mountain?

Thanks.
Chaz.