Re: Battery Sizing - am I crazy?
440AH of batteries for mostly daytripping?
You're not crazy. Get two 29D's, leave the battery switch on 'both' most of the time. When you drop the hook and there's a chance you might dawdle and run a battery down, then split the batteries, so you know you'll have one left for starting. No big deal and simplicity pretty much trumps all the theories and options.
In fact, for your use? One 29D or one 31 would probably suffice. Add a "battery brain" or other low-voltage cut-out on the positive post, and that will cut off all loads when you reach a low voltage, saving just enough battery so you can start the engine back up again. No master switch required, just reset it if you pull the battery down that low.