On a boat, I really don't think you'll see a difference b/w flat packs and standard. Most likely just see it in the batt temps. If you're already at 140F with prop X on a "side-by-side" config, then it may not really matter since you're at the temp threshold anyway. I don't think a flat pack config will cause 5F increase. Even if it does, I'm still at the threshold of being over propped anyway.

I don't see it from a performance standpoint going with flat or standard. I see it from a temp standpoint and prop standpoint. I can't go any larger a prop anyway. The motor is still running at the same temps either batt config.

Either config will fit.