The tub in mine doesn't appear to have a lip that the surround would normally fit over so I was wondering the same thing. If I calked between the tub and surround would the flexing of the trailer cause the calk to separate?
Dale & Deb
2009 Silverado Crew Cab 2500 HD
2014 Dutchmen 275BH TT
Have you noticed any moisture problems? I have installed several tub surrounds in houses and they say to caulk . My dealer said not to unless I wanted to but I don't want to if I don't need to .I hope someone with experience with trailers will respond.