Styrofoam! Of course. I knew someone would have a better idea... Thanks S Clarck.
Danny, Yes I am planning to do that mod to the brace. In fact, I actually did it to a pair of the .5 boxes but decided to go N3S instead of N2X. After I bought the .5 boxes I decided I wanted the N3S for: Higher sensitivity, more dynamics, and last but not least, the ability to convert to N3 transmission line when I can afford those cabinets.
Thanks for the help guys.
PS: Anybody looking for curved, gloss black PE boxes for N2X? SOLD!!!