Bill Crealock, in his brilliance, designed the battery box location in the port cockpit locker on the 34 so that it shared a bulkhead with the refrigerator. If you are cruising in the tropics or intend to, this fact is important because one of the more difficult things to do in the tropics is to keep the batteries cool enough to allow efficient charging and prevent thermal runaway. A friend of mine on another boat had a battery blow up a month ago. Not pretty.
As I write this, it is 100º (La Paz, Mexico). The temperature in our battery box is 78º (just checked). Two factors contribute to the cooler temperature: 1) the batteries are below the waterline and the sea temp (84º) is cooler than the air and 2) the fridge is at 35º. Something to think about.
We managed to fit three group 27 AGM's in the stock battery box (see picture at Outfitting10
) by bonding in a piece of teak under the outboard battery to level it with the others. Then we blocked it in and lashed it down with big zip ties. The box lip restrains it as well.
PSC34 #305 Swan