The reason Dicor was not used around the windows I am told is that you can't use painters tape with Dicor to control where the caulk goes and doesn't go. When you use Dicor and pull the tape off, all these gooey strings get pulled up and go all over the place. The silicone (apparently) "plays well" with painters tape so you can attempt to get a straight even edge (even though on most of the silicone applications there is a small ridge where the tape was pulled away).
This is an application procedure issue and it's not about the materials.
You don't need and shouldn't use any tape when resealing any areas on your trailer. The problem most folks have is that they can't apply the sealants correctly and apply too much, initially.
First thing is the gun--buy the better ones, not the cheapest you can find at the Big Box stores. You want one where the trigger can evenly be pulled to distribute the sealant evenly. Next, when preparing the tube for use, cut on an angle a very small hole (1/8", maximum). Place the tube end at the start of the sealant run and, while applying pressure to the trigger, draw the tube end away from the bead you are applying. If done right, this will leave a bead of sealant 1/8" wide (or so). I like to compress the bead into the joint being sealed and use a spoon, caulk tool, or my finger. Compression of the bead will force sealant into the joint and even out any untoward cosmetic issues.
Hope this helps. BTW, if using Proflex or similar sealants when temperatures start to drop, I've found them easier to apply by heating the tubes just a bit. THis helps to lower the viscosity and the sealants flow freely.
