I don't have a lot to offer, but have been doing a lot of reading on E85 as I am thinking of switchcing since I have an extra 1050.

This is off of the www.raceone85.com site :

Q: How much compression can I run with E85 fuel just the way it comes out of the pump at my local station?

A: This is one question I don't have a concrete answer for. We are running it in engines up to 14.5:1 naturally aspirated and some fairly high boost forced induction applications with great results. I have seen charts that draw the line at 16:1 but there again I just don’t have the data yet of a failure directly due to the compression limit of pump grade E85 being reached.