Hydraulic master cylinder - Firewall flex solved

Did you cut a hole for the clutch MC, or was it already there, speedo cable?
Yes, used the same hole saw I used to make the hole for the clutch master cylinder in the plate in the bracket. There's about an inch of the master housing that sticks out past the mounting plate, so the hole in the firewall has to be big enough to clear the master and the rubber boot, not just big enough for the pushrod alone. That's another reason I wanted the bracket like this, making so large a hole in the firewall, I wanted it sealed up.

The firewall there has part of the bend, so it's not a hole through a flat section of firewall, but it's the only place you can do it. I still like this a lot better than putting the clutch master through the firewall hole for the clutch throwout pushrod, which requires the cylinder to be very low, and at a very steep angle and also to interfere with the wheelwell. I couldn't see any way at all to make it fit that way in fact.

The manufacturer says you want a 6:1 pedal ratio, so that, based on the geometry, requires the centerline of the clutch master to be about an inch lower than the centerline of the brake master. Hence the dogleg shape. Now let's just hope it actually works out.