Agreed.
A low noise line is the key to getting higher and more stable syncs with a high attenuation long line, and is more important than line attenuation alone (I'm able to hold sync for longer than many with much shorter lines, and end up on a good IP profile because of the good stability allowed by my line).
I consider myself to be very lucky, in being able to sync at 4096kbps (at 6db noise margin) on a 6.9km line with an attenuation of 57db.
Admittedly, if I want a stable sync (to hold for more than a few days) I have to deliberately sync during medium to high noise periods (resulting in a sync around 3600kbps, which will hold for weeks if I leave it alone).
Ade
Giving UKFSN/Entanet a try
DL Sync 4096kbps
UL Sync 448