No you don't. Yours is sorted Tony. Your rear battery is a trickle charger - well 4 amps or so and it's never had any difficulty in keeping the LB topped up but it's a different set up on the new vehicle. This 24v start thing is not necessarily that helpful. Moral is, I think, don't be tight on main batteries on an auto 80. Three years in, change them. If the main battery goes down you could boost from this system, but if the aux starter battery goes, it's a different matter I would think. You still only get 12v when you boost, yes a lot more amps but not at 24v.
I just want to get it in and get on!
Chris