I've got one of the Z5 eccentric tools, and its a great help. But it can only be inserted when the wings are within about ¼" from closure. It would be even better if more eccentricity was present, to allow the tool to be inserted with the wings further from closure. I think the strength of the plastic tool could be maintained by putting a steel rod down the center.

Depending on the major diameter of the pin, I try to make the smaller eccentric stub as small as I reasonably can without compromising strength. Generally, a pin of 32-36 mm has a stub of around 22 mm, for about 10-14 mm advantage. I have made some pins with a smaller diameter stub, and incorporated a stainless steel reinforcing pin through the center of the stub into the main body. Naturally, this option will cost more. I also have the capability to mill a 1/2 inch square socket in the end for a 1/2 inch drive ratchet in case the handle holes (at 45 degree spacing) aren't sufficient for handle clearance inside the fuselage.