I think flat because if you raise and get shipped on your in awkward spot. not sure if its best option. the reg wont try bluff fish otr imo so river not to difficult to play.

Just my 2 cents

is he overbetting with the 200, I'm sorry but what size would the pot be ott?
If is an overbet I agree with bronxsystem and lean for a flat over a raise

Actually if I counted right and the pot is 167$ ott and good reg makes it 200$ and fish calls I could even think of a fold cause a raise would mean committing the pot being 100bb

i think call > fold > shove