Re: Derek Roddy here!
I'm obviously not Derek, but what I did was do a LOT of practice with stops and starts. Simple four bar patterns of 8ths and 16ths, so you're constantly alternating between them. I had the same problem, now it's mostly remedied because the repetition just forced my body to figure out how to do it.
As flies to wanton boys, so are we to the gods. They kill us for their sport.