Dave,

Might not be any use to you now, but i remember way back talking about this with you, as i'd got all the articles off the same austrailian site (cant even remember what it was), but i do remember them doing a follow up, and saying they changed one of the regulators as it didn't perform as well as they'd wanted.
From what i remember they had the exact same problem you've had, and switched to a slightly more expensive one which had much better control.....