I've got a OS CVA .15 powered delta with 26 inches of span. It's got stock timing, but the pipe helps a little. You got to really get the CG spot on and the control throws as conservative as you can get them to make something this small and powerful easy to control.
IIRC, all it has is a 5/32" or 3/16" FG kite tube for a spar that runs through a few 1/4" thick balsa ribs.