I need to flush my 2001 vintage fiberglass wing tanks that are assembled in the wings. I have had a bad case of the Brown Sticky Stuff (BSS) issue discussed in past threads which is gumming up my carburetors and causing rough idling. I'm removing my wings to better enable the rinsing/sloshing of the tanks. In reading the Kitfox service bulletin #60 it suggested options for aggressively rinsing the tanks, all using acetone and some options acetone mixed with AVGAS. However, at the end of the service bulletin it states that fiberglass tanks manufactured before 2007 should not be rinsed with acetone and that they should only be rinsed with AVGAS alone. Does anyone know what will happen to these older tanks if they come in contact with acetone? Any opinions on whether the AVGAS rinse alone is good enough to completely eliminate all the release agent?

I have another potential complication in that my tanks were coated with the Bill Hirch sealant that was also discussed in past forum threads. I put this in the tanks prior to installing them in the wings and believed at the time it would help "seal" the fiberglass from any possible future fiberglass release agent coming out of the tanks. I also expected that it might "seal" the tanks from any future possible exposure to ethanol laced fuel if I was forced to use some in an out of gas scenario somewhere. It's painfully obvious to me now that the Bill Hirch sealant is not working to seal out any fiberglass release agent outgassing. But it probably won't prevent the AVGAS from rinsing the release agent out of the fiberglass either. Once my flushing is done I'm wondering if I should use AVGAS exclusively for a while before switching back to MOGAS. Any opinions on that though?