@aesmith: Line 1 is supposedly in the training period heading for 6dB, and indeed it has shown entries in the clueless logs that indicate that it is supposed to be doing it, yet the SNRM is still really low around 1dB. It shows little tiny flicks of packet loss a dozen times per day, very short periods each time, behaviour which the other lines are currently not exhibiting. So I'm not really worried about it, just monitoring it and wondering why nothing seems to really affect the actual SNRM achieved. The downstream sync rate went down very slightly, for something like 2550 to just under 2500 - I forget the exact numbers - after I supposedly adjusted the target. Maybe I do just have to forget about it until the ten day period is up, at least.
Even then, I don't know that I am going to actually do anything further about it, such as (trying) increasing the target to 9dB to see if that has any effect. I wouldn't want to lose any speed anyway as it is reliable enough currently, provided we don't get any more episodes such as the two-hour-long downtime with constant resynching that happened with line three a couple of weeks back.
These modems are just very aggressive and are perhaps just a bit waywardly so. I know there are modems that can apply a kind of offset target SNRM offset parameter, for want of anything like the correct term. Bet Bt really hate that. Maybe their defaults are just a little like that, but there does seem to be more to it, in that they do seem also to be unresponsive to pressure from BT+AA to (directly or indirectly) get them to change their behaviour.