We are of one mind on the Acryl-R. I prefer Sikaflex to Vulkem, but that is just personal preference. Polyurethane sealant is the BEST!! If you want a white sealant that is 'self leveling' similar to what the factory uses around roof vents on the new units, try Dicor Self-Leveling Roof Sealant. Use it in a frame gun, and it spreads itself around the seams nicely. It is the stuff most OEM's use on roofing seams and openings.
It might be difficult to find, but any well stocked RV supply should have it. If you can't get it, I always have it in stock.
Lew Farber...RVIA Certified Master Tech...ABYC Certified Master Marine Electrician
SOLAR TECH ENERGY SYSTEMS, INC.
AM SOLAR ...MAGNUM…VICTRON ENERGY...LITHIUM & LIFELINE BATTERIES…MARINE REFRIGERATION