For all the optima lovers out there these Oddessy Extreme dry cells are the way to go. Oddessys claim is "Twice the overall power and three times the service life of conventional batteries"
And for my 95 XJ It's been excellent so far.
Accidentally left my headlights on while shopping last week , had to have been close to an hour and it didn't phase it one bit.
My only complaint would be the fact that they are super heavy. But as long as I don't have to take it out any time soon, I'll live with the weight.
Oh and let's not forget it's a dry cell, so it can be installed upside down and it won't leak. Personally I don't plan on spending much time on my roof rack, suspended from my safety harnesses, but good to know if I ended up that way, the last thing I'll have to worry about is battery acid pouring out all over the place!