What brand/number spray on sealer are you referring too? The gutter screws are part of the problem too and any spray on sealer may not correct that area. But again do not know what product you are referring too.
I did fix mine back in 2009 just I used Eternabond to seal all roof penetrations except the 2 tank vents I never made it too. This process takes some time but it for sure works. Still have it totally intact and roof leak free.
If you want to keep your camper a good long time, you are on the right track. The roof caulking has to be addressed and in top shape, all the time. And consider the Eternabond upgrade and consider cleaning the roof and treating with 303 UV protectant frequently to help with the Sun damage to any plastic, rubber or vinyl up there including good caulking and the E bond too can benefit from the 303.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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