When you get to the point of using a propane torch and a hot putty knife, cross linked does not seem to be a factor. Last year I put thin rod (1 mm) in any scratch deep enough to hold them, hit it with a torch and then used a soldering iron with a big flat tip to smooth the skegs. I did this because I am getting concerned about removing material every time I smooth the hulls

I tried plastic brazing with a soft black rod, it was not very strong. I tried hot air brazing and the skin bubbled up. A local company supplied me with a 100 watt soldering iron with a flat 1 in diameter tip and what they called neutral LDPE brazing rod.