It will be ok if short term. Furled tight n neat. Then well tied off n several places up n down the sail.
You might want to tie off the mizzen mast with some "shrouds" if it gets rolly. So as to limit the mast waving about alarmingly.
Anymore than the odd day, make sure you have a UV strip on the sail...and its furled so that the UV strip is on outside!
My BRe mizzen when on mooring, always came down and went underneath overall cockpit cover. It will stow in one piece, with just the mast foot sticking out.
I used to cover both ends of mizzen with breathable shoe bags (and the outboard end of the boom too, for that matter) as they ar3 JUST under the overall cover.
You don't want your sails to end up like the attached apparently unloved BRe seen on the pontoons in Mylor last eve.
