Blocking off runs on Morris flat fans

Has anybody had some success doing this? I'd like to try part of one field with 20" centres instead of 10"
How critical is keeping a symmetrical pattern inside the fan shape? Will I get horrible distribution if I don't redo my hoses so that things are still symmetrical when every other run is blocked off?
Or is this an instance where flexi/bg distributor heads shine a little brighter?

Blocking off runs on Morris flat fans