The following is my opinion based on my experiences with ProFlex, SikaFlex and Silicone sealants that are applied from a "caulking gun tube"....
ProFlex is a very thick "paste" that doesn't sag, is great "IF" you're an expert at applying a smooth, straight bead of sealant. It doesn't tool well and will adhere to itself, to other types of "NON-SILICONE" sealants and will adhere to wet oily surfaces as well as dry, clean surfaces. It sets up "harder than silicone" and is almost impossible to remove once it's set.
SikaFlex is a medium thickness "paste" that doesn't sag, is easier than ProFlex to tool. It will adhere to itself but will not adhere to wet or oily surfaces. It will adhere to "NON-SILICONE" sealants such as ProFlex. It sets up faster than ProFlex, usually in less than 20 minutes and if wiped before it sets up, it smears and is impossible to remove. So, apply it carefully, use masking tape if you're a "messy applicator" and remove the masking tape as soon as you smooth the surface. Otherwise, the tape will become a part of your trailer.
Silicone is a medium thickness "paste" that doesn't sag, easy to apply, easy to tool, can be cleaned up before it sets with many solvents. Once it sets up, it can only be removed mechanically (scraping/peeling) and from my experience, NOTHING sticks to it once it's set. So, it's easy to use, easy to tool, difficult to remove and hard to get anything to stick where it was. It doesn't seem to last as long as ProFlex or SikaFlex.
My personal preference is SikaFlex. If I'm applying it where I need a smooth, visible line of sealant, I use masking tape, apply the SikaFlex, tool it smooth with my finger and then carefully pull the tape away before it sets up. Since it sets so rapidly, I do a small area at a time, maybe 3 or 4 feet of bead. For doing the roof aluminum moldings, I don't worry about appearance, just clean the old sealant, remove any damaged sealant and apply an overlapping bead that covers the old and overlaps the sides of the old sealant.
SikaFlex is about double the price of ProFlex and about 3 times more expensive than HD or Lowe's silicone, but even at $12 for a tube of SikaFlex it's "cheap" considering it's a "once a year expense" and one tube will do almost any trailer. My recommendation is to prepare the entire trailer before you ever cut the tube and start using it. Once it's open, the longer it sits in the tube, the harder it is to apply. I've tried to save it by sealing the tube, freezing it, etc. Nothing seems to preserve the un-used SikaFlex, once the tube is opened, it's good for a day or two, then it gets extremely hard to push out of the tube.
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John
2015 F250 6.7l 4x4
2014 Cougar X Lite 27RKS
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