I believe if the headspace is correct and you are getting 100% of the fire going to the powder charge of BH209 then the size of the flash hole does not really matter. I just was playing some this afternoon, before I cleaned my gun, snapping primers and I really like the Rem STS's and Fed209A's in the PR vent liner of .033. I snapped a few off with the o-ring in my breech plug and on both I had a nice steady stream of fire come out the end of the barrel. This is definitely the type of primers I want to use during cold weather shooting BH209. I have one of your grade 8 Omega plugs and it fires BH209 perfectly and I think its flash hole is .028. It is headspaced for just about any primer I want to use except Win209's and the Euro primers.