I have enjoyed using MGS 285/287, but have not found a 5-gallon option anywhere (in the United States; the North American MGS distributor is in Canada). For 1-gallon orders from Aircraft Spruce, the problem is the $45 hazardous shipping fee for EACH container of slow hardener (a 2-gallon order requires 4 hardeners, 4 x $45 = US $180).
My research shows that this PRO-SET system is as good as MGS 285 which I have enjoyed using, and does not have such hefty HazMat charges. My only gripe is that I understand all PRO-SET to be shipped clear, whereas the MGS hardener was dyed, leaving no question whether the epoxy was mixed or not. Still, from PRO-SET's web page on this system I note this:
Laminating Epoxies can by dyed, upon request, to provide for visual quality control. A yellow dye in the resin and a blue dye in the hardener, when properly metered and thoroughly mixed, will result in a consistent shade of green.
I might try Wicks Aircraft for this one.