Thomson 585v7 and [xdsl.ini] maxspeed

[#1]

I noticed there is an entry in the saved configuration file
[ xdsl.ini ]
...
maxspeed tx=800000 rx=8000000
But no reference to this in the CLI manual.
If I edit the file  (giving tx=600000) and restore this configuration, is there any possibility that the uplink will be limited to 600K or, as I suspect, will it be ignored (I am reluctant to try at the moment as it may just mess up my present settings if I restore)?
I ask because I had a relatively long stable period with 650k/3250k immediately after transfer to 21CN and "training" completed, but for the last few months the link keeps reconfiguring to increase uplink speeds, so I go from something like 664k/2580k to 750k/1420k, and then upping the s/n margin to 8+db on both, slowing the downlink even more.
Current stats are:
DSL type    ADSL2
b/width        664 / 2584
atten          37.5 / 61.0
s/n margin  4.5 / 8.5
Otherwise, would there be any benefit in forcing an ADSL1 connection or asking for the uplink to be capped at 448k (which I think I read here is the only cap setting possible)?
Phil

[#2]

With such a long line you are effectively running as ADSL1 (even if it says ADSL2) - you will never, ever get ADSL2+
Perhaps a "banded" profile would suit you better?

[#3]

Hi PeeGee,
It'd be much easier to request a banded profile be applied than move you back to ADSL1 (unless we move you to the ADSL1 service still on the 21CN network). If we cap the download at 2Mb your upstream may well increase, but you're getting greater than the 448kbit that's usual on these lines.

[#4]

Matt,
Thanks for the response - I've been busy on other things recently, hence my slow reply.
Since posting, I have restarted the router and it's been at 608/2905 for about 5 days, which I'm happy with
The reason for the original post was to see if there was a way of preventing the up speed being increased at the expense of the down, which is what the automated adjustments seem to do I shall have to read about banded profiles, to see if that could be of benefit (and how to check whether I am on one or not). BT speed test gives a speed range of 600-7150, so obviously not banded
I can also confirm that the Thomson settings (ADSL or ADSL2plus and "max speed") appear to have no effect on the connection.
Phil