Frame arm length rule?

[zviratko]

Hi,
is there some sort of rule or best practice when it comes to arm lengths? What happens when one takes the flyduspider frame and makes some arm pairs longer? (for example I'd like to extend the front arms a little bit).

Does it need to stay strictly symmetrical for good performance?

[dramida]

if you elongate one axis, your proportional PID coeficients have to increase as more travel need to do that engine.