Yah Yah Good Stuff
I just did this a couple of weeks ago. Instead of drawer knobs like Mike Bullock used, I took a piece of 1/2" aluminum rod and cut it 1.5 inches long. Tapped #2-56 into the center to make a Tee-Handle on the end of the hinge pin. Used a 2-56 thread die to thread the hinge pin (hard stuff, use Boelube & go slow). I ordered thinwall stainless tubing with a 3/32 ID from McMaster Carr, and ran that from just forward of the firewall, aft to the rib adjacent the subpanel. It curves a little around the NACA vents, but no problem. Proseal was used to tack down the stainless tubing against the fuselage skin under the NACA duct. It IS IMPORTANT to have the aftmost eyelet on the cowl hinge be fastened to the lower cowl as mentioned previously. I also fabricated tiny brackets to guide the stainless tubing to point directly into that eyelet so minimal fiddling is required when pushing the pins in place.
Overall, it came out great and I am very happy with the result.
One "safety feature" of this design modification that might not be obvious is that you never fully remove the hinge pins (the front 10" stays engaged in the stainless tubing when "fully retracted", and they lay in your seat - so it would be almost impossible for you to "forget" to put them in. You know, like maybe you're putting your cowl back together and you just get the upper cowl camlocs on the firewall installed when your cellphone rings and you're called away for 25 minutes?
Let's see, hmm now, where was I? If your hinge pins are on the bench and normally install from the front it is ALMOST conceivable that you MIGHT forget to put them in on a really bad day.
I will post some photos of the final configuration when I get home tonight.