Yes I use one on my Jet. (12v)
These batteries can be mounted in any position except upside down giving you some scope to mount it somewhere other than where the battery tray is / was/ could have been.
Mine's currently a 2.8A/Hr. which is small and light enough to stow away in a redundant space but is really too small for town riding at night. (Not the best combo when using HID headlights which just switch off if the battery voltage falls below 9V.)
A 4.8A/Hr would meet most peoples needs. (9.6A/H for 6V)
Gell batteries don't really work out any cheaper. (unless you have a source)