Spoke to a CTek tech recently and he was the one who alerted me to the issue. The dual battery arrangement sort of works (but not to 100%) as the wire gauge is usually substantial and proximity to alternator is less than 1 metre away if mounted under bonnet. Batteries mounted in the rear potentially wont recieve adequate voltage to charge properly without it being stepped up.
Just looked up the Red arc product and it seems brilliant, the one bonus I see straight up is the 40 Amp input meaning 480 watts of solar panels can be hooked up. Allowing for losses means you could push your luck to 500 watts. The only down side is at this address http://www.exploroz.com/Forum/Topic/...C_Charger.aspx