Does the Pacific not chill out in the summertime? Would it be possible to hit the channel on a calmer day?
Normally summer is the time for relentless tradewinds, but I guess El Nino is expected to moderate them this summer. Winter is normally the time for lulls and brief lashings by weather fronts. I have no experience picking a weather window for a long sail, but would worry about the forecast accuracy. There used to be a satellite that gave detailed wind speed/direction maps of the whole central Pacific by using doppler radar on sea spray, but it's gone. Was especially interesting to track hurricanes bouncing off volcanos, which the weather models don't recognize.
Why not explore beyond the reef in incremental steps? In my i12s case I can normally head out to sea against the waves OK, but get spanked on the way back and have to use full rudder deflection back and forth as the swells skid my (inflated) stern into S turns. I've been thinking whether I might steer better by paddle so I don't wear the rudder setup out.
Near the windward shore the waves are of course moderated by the reef, but the winds are also moderated by running into the mountains. I'm not sure how far this zone extends outward, but sea air is heavy (temperature inversion) and backs up in a stagnation zone due to reluctance in climbing mountains. Paragliders call this a "compression" zone, but I believe that is technically inaccurate. Note how most historical wind damage in HI comes on the DOWNSLOPE side of mts from gravity winds. Counterintuitive, but windward side loses most roofs, etc during times the winds reverse direction and blow offshore.
Anyway this is to try to rationalize why the channels are more hostile than they would appear. I believe the Coast Guard gets hazard pay simply for entering the channel between Maui and Big Island. The shore of Lanai facing Molokai is filled with pulverized wrecks which that forlorn beach is named after. Well, these are due to funneling effects of hill-avoiding wind which could possibly be less with different routing. I just remember being usually lashed by water and asking the captain if it was raining. No, seaspray you idiot he implied, but I knew that and wondered if we were additionally getting fresh rainwater to wash some salt crust off clothes and glasses.
My Hobie i12s... sailboat in a suitcase! Look for it in THIS