I found foamboard at
www.modulor.de at 3,95 € for a 5 x 500 x 650 mm per shiet. I made Fuselage, FT-Flyer, Nutball and Delta-Wing out of 4 boards. Not as cheap as in USA but a lot of fun for the buck.
FT-Flyer has a span of 30 inches, Nutball 20 inches. Delta-Wing is stock with a bit of fiddeling at the wingtips.
View attachment 5386
I think a Funbat would be nice too, because there is no mixer nessesary.
have fun
Werner