I would run map 5 starting out with about 25-30% E85. Do some datalogs and check out your fuel trims after you do a couple of WOT pulls. If the trims are low, add more E85. I wouldn't jump into too much E85 and then find out the fuel can't keep up causing issues. So 25% E85, a couple of WOT pulls for autotune, datalog, see what others think, then adjust E85 accordingly.
Current: 2003 E46 M3, 2004 E46 M3, 2015 F30 335i, 2015 F80 M3