Read a little more about the sealants
739 - this product is described as a Plastic Adhesive
791 - this product is described as "WeatherSeal"
795 - this product is described as "Structural Adhesion"
My search for data sheets led to this one for 795:
and this one for 739:
Couldn't find one for 791, but "Black" isn't listed as a color so I'm not terribly interested in it anyways.
Sadly the data sheets describe different things - the one I'm most interested in, joint movement capability, is 50% on 795 and not mentioned in the 739 spec sheet. Of course the 739's elongation percent is 640%. What the difference is, I'm not sure...
The article I posted earlier also mentioned painting the inside of the plexi around the edges, to hide the sealant/tape and have the exterior look better. That of course means that the sealant will be clinging to the hull and to the paint, and then the paint is in turn clinging to the acrylic. Does anyone think that might pose a potential problem? From reading the 795 datasheet, I think it's a bad idea...
The 795 data sheet recommends priming with 1205 primer on acrylic and polycarbonate (a clear primer). Of course Dow is discontinuing 1205 production in 2010...