[TieDyedDevil]

The loop is maintained by the Boomerang. Switching patches on the Eleven Rack will have no effect on the contents of the loop if the loop is patched in at the end of the signal chain.

There's a brief sound gap (60 milliseconds, IIRC) when changing patches. You'll probably want to avoid looping that gap. Just make sure the Boomerang isn't recording when you change patches on the Eleven Rack.

The Eleven Rack may also mute the FX loop (and thus the output of the Boomerang) during patch changes. I haven't tried it, but I wouldn't be surprised if that's the case. The mute is brief, but may be noticed if you're playing a really dense loop.

If the patch-change mute turns out to be a problem, I'd suggest running the input of the Boomerang from one of the Eleven Rack's amp outputs. Then run the output of the Boomerang through your DI and into the board or your K12. That way the output of the Boomerang will be unaffected by the mute during patch changes. The only downside that that you'll need to adjust two levels to keep the Eleven Rack and the Boomerang balanced with respect to each other.