Steven,
I understand your question as about wings with both the leading and trailing edges swept forward...
However, on a technicality, even a Ringmaster wing has forward sweep! Sweep angle is measured at the quarter-chord line. A Ringmaster, Flite Streak, or any other wing with a straight LE and a forward tapered TE is mildly swept forward...
When you get to a layout like deBolt's Sportwing, you really got forward sweep... Several of Bill Werwage's stunt designs have a forward sweeping flap hingeline, btw...
A foam core wing sheeted with, say, 1/32 balsa, or glassed and vac-bagged, or either or both, in combo with CF reinforcement, should stand up to just about as much as any other way to do things. Do it strong, though. A thing called aeroelasticity does exist. Roughly, it deals with the tendency of airloads to distort the pieces we are moving through the air.
A radically forward-swept wing layout, pulling a lot of lift, can tend to twist at the tips towards MORE lift, which feeds on itself to go worse. A swept-back layout, pulling a lot of lift, would more likely tend to twist towards unloading the lift - reducing the load.
When the sweep angles are moderate, it doesn't make a whole lot of difference, but at extremes, it might just. Renger's SkySport has definite, but not radical, forward sweep. It was in Model Aviation last year, I believe.