I believe Dick Deaver or someone from the North loft tried that back in the late '60s with a Cal20+. Not masthead, but had a small sprit w/more SA. Don't remember if the 20+ had a taller stick or not.
Mike George won his class in the 78 or 79 (?) MDR to SD race flying a masthead Cal25 chute on his 'Standard' Cal20. Said he was lucky the rig didn't come down...