Looks like the Gill 242S has been superseded by the Gill 7242-14. Looks like its a little heavier (27 to 30lbs), but its has more cranking power (10amp/hour to 14amp/hour). I like that, even though I use a battery minder to keep mine charged, I found it was pretty easy to drain the 242S trying to start the Skymaster's two engines, if they didn't start right away. Especially the rear one.
http://www.gillbatteries.com/Products/Details/7242-14