There seem to be quite a few people who are running 2208s on 6045 for their 300 frames, with KISS 18a. So I'm guessing you will be ok, Kiss escs are rather beefy and the components in the 18a are rated for 30a, its only the traces for under 30a.
If you are a bit nervous you could just wait for the 30a versions, they will take 6s as well.