Don't remember the Israelis having much of a problem with F4 v Mig 21.
In my experience the avionics in the F4 gave it such a technology edge that it more than made up for size and turning deficiencies. Add the capability of a face shot that the Mig did not have and the advantages were overwhelming. Nevertheless, any crew stupid enough to turn and burn deserved to lose - unless they knew their adversary pilot was equally inept.