My boat does not have that sticker on it, but the boat is made of polyethylene (Ropolene is a tradename and is a fusion of "rotomolded" and polyethylene), not acrylic. You will not find any plastic named Ropolene. The only acrylic on your boat is the windshield and any other optically clear plastic you may have.
Anyway, polyethylene is pretty close to indesructable by any cleaner or solvent you might try to use on it. This is what
http://www.mindfully.org/Plastic/Pol...ene-Family.htm has to say about polyethelyne:
"A waxy, translucent, somewhat flexible thermoplastic, prepared by polymerizing ethylene at high pressure (1,000 to 4,000 atm) and high temperature (180 to 190 deg. C.) in the presence of a trace of oxygen. It is one of the lightest of the plastics, having a specific gravity of 0.92 to 0.93. Below 60 deg. C., polyethylene is insoluble in all solvents and is resistant to the action o f most reagents, other than strong oxidizing acids. Above 115 deg. C., the polymer changes from a clear solid to a relatively low-viscosity melt. At this temperature and above, exposure to air causes relatively extensive oxidative degradation, unless antioxidants are included with the polymer."
Most likely Triumph has added antioxodants to the plastic because you can weld it without any oxidation ocurring.