Midpole snuffers are known to scoop decent amounts of water at times. Going downwind in strong winds and the mainbeam is often quite.. Wet.. Especially when punching through waves downwind. As the spi hopefully will be set at that time and there is sufficient drainage, I would not worry until I caught something big and bad in there like a tiger shark or man o' war.

BUT, nobody knows until it has been tried. Wayne, I cheer you on!