Prepped all the parts for the firewall today. This included a lot of countersinking. I mean A LOT. Some people use wood to support their pieces but I just used my hand. It's a method I have been using all along as I have pretty much always done it this way. You get a good grip on the cage and can hold it perfectly square and you can just let the bit do the work.
Albe very careful about what you counter sink and what you don't. There is a double on the left side that will be countersunk on the opposite side of the firewall, so you don't need to dimple the the holes in the angle that intersect those rivets. Same think on the right side with the battery cage at the top of the firewall. What I did was I looked at the next section to get a better picture of what will happen and why some are dimpled and some are not.
After I finished that I primed everything and began dimpling and prepping the stainless steel parts (which do not need to be primed). I found the 3M wheel worked the best on the edges so as not to ruin my deburring tools.
There are a few simple assemblies before you begin the very difficult back riveting section. I actually was not able to finish the backrivets with my set up. Due to the geometry of the firewalls that have ridges in them as well as flanges. I am considering using my C-frame to get the missing rivets.
Things I did learn were to take out all the clecos. Do not leave ANY space at all or they will set high. Also, the AN425-4-4 rivets are correct size. If they are not legal then they are either over driven or they are not sitting perfectly flush.
So far so good. Hopefully I will figure out how to finish the rest tomorrow.