I have additional information on adhesive sealants for use on the vinyl roof. DRV's Tom Peck has advised using SikaFlex
http://www.sikaautomotive.com/ind-au...oduct-flex.htm. I found Sika products at Home Depot but not SikaFlex.
I spoke with an associate at Home Depot and he was very high on the Sika Construction Adhesive. I bought some but on review of the technical data sheet I will return it.
I have decided to use the 3M 5200 Adhesive Sealant - fast cure version. It is a marine product for through-hull fittings and I have experience with it. It also is considered permanent. It is good stuff. The brackets I am installing are permanent so that is not such an issue. It will soften with heat to make removal somewhat easier and there is an expensive solvent that will break it down entirely if necessary.
Mike is right -- any use of adhesives on the vinyl roof and subsequent attempt at removal will most likely result in torn or otherwise ruined vinyl. Do not use these products unless you intend for it to be there forever.
Bill, the self levelling sealant such as Dicor Self-Levelling Lap Sealant is not an adhesive -only a sealant. You are correct that it is easy to remove.
Thanks for the replies.
On Edit: Modified references material for Sika Construction Adhesive and added SikaFlex which is produced by Sika's automotive division and recommended by DRV.