Here's my experience with the RV-12 LEXAN window at 4+ years / 625 hours / 90% mogas 91 with 10% ethanol: I installed the LEXAN window in accordance with Van's plans (i.e., fuel sealant in and around all aft edge screw holes and sealant between LEXAN and aluminum fuselage panels). I have been careful not to spill any fuel near the LEXAN. If you look carefully at my rear window you will find very minor short crazing spikes emanating from 2 - 3 screw holes (maybe due to stress as opposed to fuel). I have seen very heavy crazing on a number of unsealed LEXAN rear windows. I have no experience with overlay films -- my understanding is that the LEXAN we get from Van's has a fuel-resistant coating on the surface but not the edges or in holes thus the need for sealant in these areas.
David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B) - N124DH flying since March 2014 - 635+ hours (as of May 2018)!
through June 2018.