balancing radiator old subject but question

Hi I have read loads on balancing and think I understand it quite well but I still have a problem.

Boiler is on 2nd floor (attic conversion) and I fitted a large upright radiator (7000BTU's) on ground floor. I ran 22mm as far as possible and last 2 meters or so in 15mm. All rads have thermostatic valves fitted except bathroom towel rad.

It seemed to work fine but now is only luke warm, now that weather is getting colder, so I read and started on balancing.

Main problem is that I am struggling to build up a 11 deg C temperature difference between flow and return on the other two on the ground floor. If I do nothing I find flow and return temperatures are very close. I find I have to virtually close the lock shield valve to achieve this 11 deg C difference and then the the rad doesn't seem to get as hot and the room doesn't really get warm even though the rad is still quite hot.

When balancing what percentage would you say the valve should be open? I know it will vary but can you give me a ball park figure because I read somewhere that it may be around the 50% mark whereas, as I said I am having to virtually shut down the lock shield valves to get the ideal 11 deg C. Should I expect it to be nearly closed or open about a turn or so?

Any help appreciated.

Try:
Small rads near the pump, 1/4 turn open
Bigger rads near pump, or smaller ones further away, half a turn open.

Once you're at a full turn to a turn and a half, most rad valves are pretty much fully open