Hi,
It would be worth a try.
Strange that the opto triac is not working, the only thing I can think of is it is limiting the current through it and so the mag field in the trigger transformer does not change quick enough.
The SCR should work, as that is what is used in automotive timing lights to trigger the flash, a timing light is just a glorified version of what you have, just being able to flash very quickly.
Tom.... 