The bandit 3 9m uses a 45cm bar which is probably a little bit short for a nice use of your 12. It will work though but your kite may turn too slow.

F-one use to have their own length of lines but if I remember well since the release of the B3 they've been using a standard set up which is compatible with most kites on the market.

F-one kites flag on both center line so you'd better check if the Switch kites work the same. If they fo flag on a single line then the F-one bar set up is not ideal for using it on a Switch kite as your safety may not work. The other way around would work but as you are asking here is the answer.

Check for the pig tails and lark heads as I think F-one has 4 lark heads on the lines side.

Hope this helps