Thx for the answer. After hours of googleing I found the solution, sometimes is simple.
I add following lines to the oscam.server (add to both reader configs)
[reader]
ratelimitecm = 2
ratelimittime = 10000
srvidholdtime = 5000
I run some test, watching two channels from first reader with valid subscription, select a third one = no descrambling of third channel, no breaking rules, no violation, no requests rejected.
Second test, again watching two channels from first reader, select the third channel from free test reader = working with second reader.
As I can see in Oscam log, with two different valid subscription for two reader, theres no error. Think this can be the solution for all Quad tuner user here, record or watch 4 different channels without breaking the rules.
btw. I use two twin tuner (Wetek Play) connected via SAT>IP, they act as one quad tuner. So with this solution, more then 4 channels are not decoded and no danger breaking the rules here. This prevent other user with dual or single login also for breaking rules, with single login just change the line
ratelimitecm = 2
to
ratelimitecm = 1