I've found that the trigger pulse can be as narrow as 5uS; therefore the flicker you refer to is imperceptible.

Also, you could put in a line that caters specifically to this situation; e.g., if X = (1000-X) then High Out1 - Pauseus 5 - Low OUt1 - High Out2 - Pauseus 5 - Low Out2.

BTW, I am using traics, not SCRs. Any particular reason you are using SCRs?

Regards,

Anand