Times three for not using silicone. It just makes me cry when I see where people take what they have on the shelf in garage or the home improvement store and use it on their RV's.
I'm just now in the process of repairing two older RV's side by side myself. And I'm a firm believer in using the right product and the right color to keep it looking nice.
If I'm not pulling out the window (a huge undertaking) and replacing the
Butyl Tape, only resealing it from the outside, then carefully use a putty knife to clean out the old sealant that is weathered and replace it with
Dicor.
Another sealant I'm a big fan of is
Sikaflex 221 and it can be found at most RV shops as well as Camping World. It is super strong, works like epoxy in terms of strength, and stays nice for many years of exposure.
Silicone attracts dirt, discolors over time, and is huge mess to clean off surfaces down the road when more sealing needs to be done. Good luck with your project. All the best, Hans