Do Group 27s fit?

[FCStreamer]

Well, on a 30' 2014 Flying Cloud they do.

Barely.

You'll have to jiggle them to get them in there, and you'll have to remove the lock as the lid won't close. The batteries are too tall.

I also got a dual battery tray from Bass Pro Shops. It has to be a minimalist tray. Any lip on it and it won't fit.

I used the same retaining screw to hold them in place.