Two radiators in one room, one is poorly heating up Comap TRV

I recently had bought a Tado thermostat in the living room with two TRV's with two Tado buttons on it. The radiator in the front heated up really well but the one in the back did not. It took some time to figure out what went wrong. The TRV's I did install for the job were from Comap.

After struggling with the problem I found some information that it is possible to tweak the flow of the TRV with a key. It is also possible with a pair of pliers. When you look to the pictures below there are numbers 1 to 6 visible and there is a flat side on the outer pin of the TRV. When this flat side is turned to a higher number the flow through the TRV is increased.

I hope that this will help other Tado users.