CFMM between two tokens (FA1.2 / FA2 each) using the isoutility curve U(x,y) = (x+y)^8 - (x-y)^8 This curve has the benefit of being extremely flat around x = y, at which point dx U / dy U = -1. This makes it suitable to create a CFMM between two assets which ought to be pegged to one another.
Based on the generic cfmm in the ctez repo which is itself based on dexter v2.
Barely tested!
To give some sense, when the two assets are held in equal amounts, 78% of the pool can be bought for a slippage of less than 5%.