I have just switched to a Miata battery from Westco. I wanted to lose some weight (42lb to 23lb, or so), take up less space and have the option to put it in the left rear cubby-hole in the hatch. The Miata battery is made to be mounted in the trunk of a Miata, so it is sealed for interior use, and only has a pair of breather tubes that need exit points. As per the folks I spoke with at Westco, it rates just fine for use in our application, as well it should, since the 1.8 Miata uses the same powerplant we use. So far, I am quite happy. As for moving the battery, I am trying to find scales suitable for corner weighting the car, before I move that much weight from over the front wheels. If it is best left in the front, I will scoot it to the far left rear corner of the battery tray and use the space for a straighter intake tube.
Oh, yeah, the battery is a glass mat cell that is soaked with the electrolyte, so it is neither a gel cell, nor a wet cell. The price is about $85 US.