Replacement gunnels out of 3" square housing pvc pipe?

Good idea,but I thought foam would melt if it came into contact with resin?
I suppose another method would be to cut the outward facing fibreglass on the gunnels off,and f/glass over the gap once the
timber was removed.
As you can see on the pics,the gunnels are pretty robust.Seeing as it's only a project,I'd like to keep it looking as is.

 

That depends on the type of foam and resin.