In order to understand the position of the rudder pedals relative to the firewall, I temporarily installed the vertical stabilizer and rudder.

With the rudder stops in position, I took measurements from the cable attachment holes of the rudder horn to the aft end of the control cable fairing.

Here are the measurements. So, worst case, it looks like the rudder pedals will swing forward by ~2.5" at full rudder deflection. I put the pedals in the forward-most position and verified that with the rudder pedals in a neutral position, roughly splitting the difference that the left and right pedals are angled, there is plenty of room for rudder pedal deflection without running into the firewall or anything else.

I clamped up the rudder and brake pedals so they were all lined up in the neutral position.

I modified a bolt shank to use as a scribe in order to mark the location where I need to drill.

It might be hard to see the little scratch I made, but on the left pedals the drilling position appears to have good edge distance.

But, the right pedals need to be drilled quite close to the edge.

Not being happy with that, I decided to make some little stop tubes for the brake right brake master cylinders.

Okay, these should reduce the extension of the master cylinders by just over 1/8".

So, I took apart the right brake master cylinders.

Hrm...two problems.

I also noticed that this one cylinder rod has a nick in it. Fortunately, it's below the cap O-ring, so it won't cause any damage. This is a manufacturing defect since it's apparent the shaft was dinged before it was centerless ground.

I removed one of the O-rings and used my little USB microscope to see if I could discern whether the discoloration is corrosion or just grime. Looks like corrosion, but still kind of hard to tell. Let's zoom in closer.

Yep, definitely corrosion. Well, that's the price of taking so long to finish the project. It appears all of the bare aluminum parts have similar issues. I'll call Matco to see if I can get replacements.