Have been using "regular" flex coat but just picked up some lite flex coat. Want to use the lite to apply after 1 coat on regular. any problems applying one or the other over/or under the other?

You'll have no problems with compatibility, although there may not be much point in it unless that's just what you have on hand. You can apply the regular either thick or thin, although the thin (lite) version cannot be applied very thick in a single application.

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Bill,
To follow up on what Tom said about not putting the lite on too thickly, I did a butt wrap and deceided to put on a heavy coat of the lite to save some time. I had a good wrap finish and no air bubbles. I use an 18 RPM drying motor and everything looked great. Next morning I checked the wrap and had sags in the finish...looked like bumps on an alligator. A heavy application of the lite-at least for me-will not level out. Two light applications will give you a good finish.