I want to add my experience being motivatied by Godzilla's mod.
The stock Yasua is 210 CCA. I bought a Fast By Gast Hayabusa battery (see
Fast by Gast Pro Battery & Yuasa Mainteance Free Battery for the stock battery, Fast By Gast, and the Fast By Gast Hayabusa batter.
The Fast by Gast Hayabusa is 380 CCA, which is considerable over the stock 210.
I bought it on a website that did not tell me that I had to mod the stock to fit it; I have a drag seat, so I could not mod the seat.
The battery sat until I saw this post.
With great fear and trepedation, I got my dremel and set to work. Fortunately, I found the fast by gast battery fits very very snug tipped over like Godzilla's battery. Bettery yet, the FBG battery screw attachment is much better than the stock one with the nuts that have to be held in to attach to the screw.
The battery electrical attachments fit well, you might have to snap off the nearest zip tie that ties the cable to the metal frame.
I think it is a bit narrower. This means that I was able to fit it like Godzilla, but I did not have to use a bracket.
I cut the plastic inner wall right below the plastic part that the ECU rests on. If you cut it there down to the bottom of the stock battery tray, you can fit the FBG batter snug and then when you fit it in there, you can "pop" it up and now the rear of the battery rests on the other side of the plastic part that holds the ECU. This holds the battery sung.
See the pics attached. Post here if you want any more info. Thanks to Godzilla, and basically, my mod is his mod with the FBG batter that I think fits even better since is cut looks like it is above the ECU plastic holds. It does not stick out far at all.
Finally, I decided to mount the license plate using the stock mount (on the underside of where the ECU lies). If you reverse the stock mount, it lies just right with a good lean.
I hope that anybody that wants to install a larger battery finds this helpful.