I think what I’d do if you are looking to have a spare backup keyboard or need an arranger in two different locations would be to sell the BK7-m and look for a used good condition BK9.

That way, a) you have a backup, b) you have 100% data equivalency.

There are a lot of sounds and kits in the BK9 the BK5 doesn’t have, so you are likely to need to do quite a bit of work in the Makeup Tools, and you’ll have to completely redo your Performance Lists, because the BK5 cannot read BK9 UPS’s…

There’s a lot to be said for not having to do everything twice!