Damn, I forgot the helm is totally different
Not sure how much air space could be built into an enclosure with the new style helms but something in the OB should be doable to support an SPL type sub.
I've seen several done that way with a port cut into the fiberglass of the OB so sound can get out.
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2017 Moomba Craz Surf Edition
Flow 2.0 Surf System w/ AutoWake™
5,600 Lbs Ballast - Enzos + Lead + Sumo
Wet Sounds REV10s + REVO12-XXX