Proflex RV Sealant will not adhere to any sealant containing silicone. According to their website (
www.geocelusa.com),
"The most common reason a product won't adhere to a substrate is the presence of silicone from a previous application"..
This would mean that you would have to remove and thoroughly clean any silicone-based sealant before applying any other type of sealant - including one that contains silicone. As has been pointed out, silicone won't adhere to silicone.
Which brings me to ask...why does anyone use silicone in the first place when it seems like there are other and perhaps better products out there?