Well I stumbled on some photos that has made me take a second look at this.
http://vintageaircraftmuseum.org/aircraft/restoration/hall-springfield-bulldog/
Click on the photos and you'll see the shots. Most noticeable is the exhaust coming out of the cowl. I was guessing it was piped out under the cowl some how, not through. So I've already marked off on the cowl where these holes are (notice they don't have a exhaust port at the 3o'clock position, guess to keep pilot vision clear) but now I need to find some 2.mm brass pipe and get it in.
Also notice how the flaring is at the landing gear fuselage joint...since that's already attached, it may be ignored.