Hi Scott,
For what it's worth, I've always used an Interstate Cycle-Tron (Yuasa) #YB9B in my Harris (which has the battery located in the "proper" location), and they've never let me down for ignition and starting, even when I used to run total loss. I do keep it on a 2amp charger when in the pits. It would fit the opening in your seat, but might be a little tall at 140mm. It's also old school construction, meaning heavy. I was going to look into something lighter for next year and I'm also going to need something for the Adamo 851 I'm rebuilding. In the Feb. "Motorcyclist" that just came, on page 8, there is an ad for Shorai Lithium batteries that caught my eye (maybe it was the model in a bikini) and checked their website (below). For a Ducati 748 they list two, a regular and a racing model which is even lighter and for less money. Does anybody know anything about these? They're not cheap, but nothing extra light is. They look almost like a traditional battery, so they might not look out of place on an older bike with great style, like a TT.
Bill
http://www.shoraipower.com/default.aspxI just looked up the Shorai replacement for a Yuasa YB9-B. The race version (#LFX07A2-BS12) weights 4.83 lbs. less than the lead-acid YB9-B at 1.01 lbs., has 102 cranking amps, costs $99.95, and is a smaller package: 113mm x 58mm x 89mm tall. Hmmm....I likey.
Bill