I don't know if Mas publishes their numbers, but most room temperature epoxies soften by about 150F, and will retain their properties on cooling. If you exceed that temp, say past 180F, especially if you do it rapidly (like quicker than 10F/hour), the epoxy will likely be made brittle. Your call if the fillet is in a critical location, and if a lessening of its properties effects your craft's integrity. A short segment, especially if you are adding tape over it, is likely fine.

A slow ramp up and hold to 130-140F is a good idea to post cure the finished kayak, before final sanding and varnish, to avoid later print through as the deck cooks in the sun during use.