Jim
The Roma cars (G.A.T.X 944 and 985) I have seen pictures of were based upon a GATC design which differed from the Thomas design which appears to be similar to ACF six-dome cars. ACF did build a number of six-dome cars. There has not been any really accurate models done of the GATC cars. PSC imported them years ago in HO and O. They made a significant error in that the domes have a flanged base with rivets around the perimeter. The actual dome were insulated and mated with an insulated body. So the dome attachment point would be hidden.

Gene Deimling