So (if I understand this correctly), because your sync speed is right on the border line of one of the DLM speed profiles, the DLM chops and changes your available speed by as much as half a megabit?
I'm not sure there's much you're going to be able to do about that, except move to an ISP that doesn't use BT back haul network (and hence no DLM).
If you can switch to 21CN, there might be a chance the DLM will put you on a 3db noise profile, with a higher sync speed, but that's likely to make things more unstable. You could try and counteract that by switching on interleaving, which will increase latency.
Food for thought.
EDIT: I think the 3db noise profile is only if you sync using ADSL2(+), so if you only have an ADSL1 router, forget that idea - or buy a newer router.
Edited by mixt (Wed 17-Aug-11 21:12:04)