Loose Rig Sails on a Snug Rig in heavy air

I recently changed my rig to snug and bought a new set of MAD sails for snug rig (The performance of the boat upwind has really improved!) My B-sails are now my old (loose rig) sails which I intend to use for heavy air days (>15 mph)... I want to understand what is the potential issue with using the loose rig cut jib on a snug rig in heavy air? Any comments/insight would be appriciated!

-Rob Hayes
FS1878 "Bad Haggis"