I was fooling with some of that this weekend
Tony,
I'm at work so I can't give you the exact measurements but I was doing some preliminary work on the hinges in anticipation of putting on my engine mount.
What I did was hold the bottom cowling against the firewall and make marks on the firewall where the top hit. I also made a mark at the bottom at the firewall where the exhaust recess is to get a feel for the lengths for each side there. I looked back at the rivet callouts for the firewall to see if I was in the ballpark. I used one shorter rivet each side on the bottom firewall row then the callout stated because of the where the recess on my cowling was.
On the side I used a shorter rivet at the most bottom rivet position and didn't allow the hinge down this far. I did this because of the way the skins were all intersecting at that point. On my sides the hinge runs from the rivet above that point to my top mark. I know I will need to trim the hinges later when I fit the top cowling but that got me in the ballpark. I will wait to rivet these in permanently when I get the top cowling fitted. According to plans the hinge that keep the top and bottom cowling together needs to lay a top the side firewall hinge - at least thats what I gleamed from the plans.
For the top cowling at the firewall I plan to use screws and floating nutplates instead of the hinge - similar to the milspec concept - so I haven't done anything there yet.
It looked to me that there isn't much room to rivet these pieces in place, especially the bottom hinges, once the mount is in place so I was trying to be pro-active.
If nobody else chimes in I can get the measurements when I get home this afternoon and submit another post - at least the ones for the bottom cowling.