So it means that twiking a bit we can fit the larger battery into the Bonneville se 11 model correct?The YTX12-BS is indeed the battery fitted to carbed models from the beginning of production until the EFI models came in around 2008-2009.
On those it was replaced by a slightly smaller one, the YT12B-BS, which is 18mm narrower, this created room for the EFI system's ECU.
Following starting problems the Factory carried out some mods to the airbox and wiring layout to make room, once again, for the original YTX12-BS. This happened around 2011. On the SE model, for example, this was from VIN number 463262.
Note that the Yuasa site search feature is not very good, at the moment it gives me a YB9-B for any year, you might as well ask the cat...