I'm in the process of building a mock-up of the GP-4 cockpit from the plans so I can sit in in and dream of flying it. I'm also using it to plan the panel and therefore the underlying systems. For instance, I know it's going to be an electric panel with no vacuum systems.

But the main reason is to design in the creature comforts for flying decent distances. I've got about 1000 hours, mostly in Mooneys on IFR cross-countries of 300 to 550 miles. I've flown Pipers and Cessnas as well. But the best cockpit I've been in so far was the SportCruiser (formerly the PiperSport) with a cockpit width of 47 inches.

Yes, that itty bitty Rotax powered featherweight was 47 inches wide!

It was plenty of room for me (5'7" 170lbs) and a large instructor (6'1" 195lbs) and we weren't constantly rubbing elbows. Even my left elbow from the pilots seat had plenty of room. There were storage areas between the seats with the center console being about 4" wide on the outside with an armrest on the top. I think I remember side pockets on the outside stations that also had armrests, but I might not be remembering that correctly.

I have no real desire to do anything crazy with the GP-4 in terms of major redesigns. But some of the minor things like this seems "safe". I also don't think it will affect cruise speed much since the increased frontal area will also be very minimal.

Has anyone else thought through this exercise?

Here are some things I've thought about that might need to be changed to accomodate the width change.
- T-18 canopy would need to have 7 inches added to the width. Is that even possible?
- Everything from roughly station 0 to roughly station 70 would need to be proportionally increased in width.
- If I don't change the length of the spar, I wouldn't need to change the length of pushrods or gear. However, if I did, I would need to add 7 inches to all of the systems that cross the centerline.
- I don't see any reason to change any dimension forward of the firewall or aft of the baggage compartment.

I'm not an aeronautical engineer, and I will seek out a proper authority before cutting any wood or metal. I'm still in the "thinking/planning" phase at this point.

Mark