Hi, when I got my Janome 8900QCP, also a 9mm machine, rather than replacing all those specialist 7mm feet that I'd accumulated, I bought an extra 'ankle' for a 7mm machine. This 7mm ankle thing fits easily into the shank of my 9mm machine and all I have to do is remember not to exceed the stitch width capabilities of the 7mm feet.
Saved me a fortune.