As you can see its compatible with fiberglass.
I too read much about the disastrous results with silicones and fiberglass together...
At the risk of wrathful indignation from the butyl purest who beat the drums of anti silicone warnings I flatly say I have had no problems with silicones as long as I choose the correct silicone chemistry for the correct applications....Silicones come in many complex chemistries so there is reason for confusion...The sealant may not make a good adhesive for instance, yet a silicone rated as both may be great but not on some materials over others when that material is not specified in the label recommendations.
Silicones clean up well between uses, they take a high heat well where butyl craps out at about 180 F, the flex in the right product is unparalleled.
The new urethanes for marine applications do work well but are tacky enough to be a problem for myself.
Most shops fall
victim to the recommendations of "sales" representatives of wholesalers who peddle this or that...When visited I ask for the specification sheets and test data sheets and the M.S.D. sheets before I consider it as a part of my operations.
I would argue that fiberglass trailers should NOT be treated as R.V.s in the classic sense of the traditional use of sealants and bonds, rather I argue they are more like boats, think land boats if you must...The technology employed needs to come from that sector in regards to bonds and sealants is my belief.
I do want to blow up the myth that silicones are evil where fiberglass is concerned...
In 99% of the cases concerning material incompatibilities the information about the product was either not understood or ignored...Silicones like plastics are a broad category of chemistries, like different plastics silicones need understanding before application begins in any job.
Happy Camping, Safe trails.