So why did they not have option C: put the revi in the centre line? It disturbed neither the Spit, the Hurri or the Stuka pilot to have the revi in the centre. Why satisfy with a second best solution (assuming that the circle as seen by the pilot was offset)?

For me the answer is clear: because there was no need for option A, B or C as the pilot saw it in the centre and therefore where the most appropriate gun convergence was.