Whilst SRA was supposed to be a fix for this issue, its been reported to not be reliable and cause more problems. (Bulldog did some tests before launching). It could be that Sky tested the router with their DSLAMs before launch and found it worse.
The ISP is supposed to set quite a high target SNR margin, for my bulldog connection this is 10db, to allow for the fluctuations you see. This gives me 12mbit sync. I know my line is stable, with no day/night changes, so I locally force my speedtouch to 6 or 7db, giving me useful increase.
If Sky have the target SNR on your line set too low, then either you can try overriding your router locally (which I think you are). I'm not sure if the Sky Netgear remembers any local override after a reboot, which my speedtouch does. Of course you could also talk to support again - with the risks that carries!
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James on
Bulldog Unlimited Plus (ADSL2+) - SpeedTouch 516v6 & Draytek 2900VG
18mbps sync at 820m from exchange - down: ATT 25.0dB, SNR 6.5dB, Pwr 23dB -
SpeedTests