Resealing/reglazing bromar hatch

[crazy charlie]

I have a good size hatch that the lexan has loosened from the rubber gasket.I need to remove from the gasket ,clean and reseal.The lexan fits into the rubber gasket nice and snug so it barely leaks.I have a good idea of guessing what sealant to use but was reaching out to someone that has done this before and knows what to use.Charlie