Hi,
If you think that C1 and C2 are still a problem, just make them bigger - all that'll happen is the circuit will take longer to stabilise. As long as the signal on the +ve end of each capacitor never rises above (or falls below, depending on sync polarity) the logic threshold all will be well - i.e., the logic level as seen by pins 2 and 5 of the gate should not change at all once the circuit has stabilised. The values were calculated as conservative for 405-line, so will be ok for 625, 819, etc; but C1 and C2 may need increasing if you use it on slower standards such as 240-line - depends how conservative I was, they might be ok
Regards, Kat