Truewind, I was just given a Sumner-8, which sounds exactly like the boat you describe. The sail rig on it is a sprit sail. My sail rig is missing the sprit but the mast, sail, and boom are all there. I could not find any info on the boat either. I posted a question on Woodenboat Forum and got good pictures of the complete sail rig. Follow this link to the thread:
w w w . w o o d e n b o a t . c o m /forum/showthread.php?t=86430
Take the spaces out.
That forum is where I lurk, and the best place to reach me would be on that thread. I can email you pics of my boat and take dimensions if that helps you. Maybe we can help each other get these boats fixed up right.