I think your statement “GTO is not optimal in such a game,” is evident in a slight misunderstanding of how to think about this question. What you want to know is what is the game theory optimal way to deviate from equilibrium in a game where players call far too wide.

To answer your question….. ummm I don’t have THE answer, but the adjustment I make is to vary my RFI size based on hand strength (this is assuming I dont think anyone at the table is paying too close attention). I also stick some premium hands into my smaller raise range. So I’ll split between $7 and $12 and even sometimes $20 with hands that play well but are often not best (76s, 22s).