I have just built the XSCat by J. Turner plan available fro Traplet https://sslrelay.com/s84068217.onean...dex.shopscript

The sponsons are foam cores covered with 1/32 ply but glass would work too, you could probably cut the center section from foam as well. I shortened it to 24in too fit my foam and widened the center section to take a 700 and 12 cells, as I plan to race in a restricted class (SWAMBC F4). Last weekend I ran it with a Mega 22/20/2 and 12 GP3300's to find the limits of the handling, it was quite rapid (mid 30's) and I found the rear limit for the c of g !