Read the posts suggesting upgrading to a 51r, so I went out and bought one. Didn't read far enough down to see that it's not a drop-in replacement, and usually requires some extra rigging. I think I have found a way to install the battery without any extra cables or terminals.

I removed the battery tray. Might decide to cut the sides off and re-install later, but for now, it goes away.

Cut away the stiffening ribs on the airbox. Wire dikes worked great for this. This gives enough clearance for the positive cable without any alterations or adapters. It's tight, but it fits.

Shimmed the battery up 3/4" using some scrap flooring. Necessary to get the positive terminal clamp on.

Re-installed the stock battery tie-down clamp. there's enough length on the threaded clamps.

That's it!