I have a set of plans for a 66" Ryan model aircraft. The plans are by Henry Hafke and I bought them from MAN's plan service, Air Age I think. There is a drawing of a Kinner radial on that plan ( I am building the Menasco <sp> inline engine version). It shows you how to construct the Kinner radial with balsa and ply and it subs in the glow engine cylinder as one of the Kinner cylinders. Not sure if this is large enough or scale enough for you, but might be. Lemme' know and I'll mail the Kinner radial plan to you.
Jon