I was looking over what I had to do to the motor box on my GP Pitts, and decided to check the
6 1/2 dimension given in manual. With the cowl setting againest the end of the Fuse, I'm getting
about 6 1/4 inches. It shows the cowl mounted back about a 1/2 inch. This would make the the
6 1/2 dim. way to long. The photo of the OS 1.6 does show the prop washer sticking out about
1/8 of a inch. Has anyone found this dim. wrong also?? I'm going to have to alter the motor box, by shortening it, so that my Saito twin will fit. The Saito is 6 7/8 overall in length, from prop washer to mounts. I know most people are mounting gas engines, which need spacers to get them out far enough. I just wanted to hear from you guys who have built this plane, did you have a problem here?
Rick

So, What did you set the prop hub to the fire wall? I know there are alot of Piits out there, and had to find an error in the instructions.

Mine is mouted at 6 1/2" from spinner backplate to firewall. My cowl overlaps the fuse by about 1/2". You may need to cont GP and see if your motor box is constructed wrong, if it is a new kit. If you purchased as a used plane, possibly someone has altered it to suit their install.
Can't say for sure.