On the more extreme side of things, when we ran an all iron 301ci SBC on 95% nitro in my high gear car, in the mid 60's. We ran a some what odd ball combo; 10.75 to 11.25 compression, a 110 Enderle fuel pump, that Kent Enderle said it's too big, it's a pump the top fuel guys were using, not a unblown 300" SBC. But how we got it to work is our Vertex mag had 20° of advance on top of the 55° static timing we set it with, which Kent said 55° was about the JF cars were runing at Lyons. Yes, we had to push start it faster, but we ran 191mph in 1964, running 75°, with a "Too Big " pump.
On the west coast a number of FED are running under 20% with 12-1 compression racing in the 7.60 class. With 14+ pistons I agree with Spud, you will have detonation, and blow head gaskets, running 20%.
Jon