dimpling firewall flanges

In section 27-04, the plans specifically say not to dimple the firewall flange holes. I would imagine this is because we need to use those holes in section 29-08 to match drill the holes in FF-00006B hinge and F-14134B hinge shim.

After match drilling the hinge shim and hinge, section 29-08 has us dimple the holes in the hinge shim and countersink the holes in the hinge. The holes in the side skin were previously dimpled.

I don?t see where we dimple the holes in the firewall flange. Since the flange is sandwiched between the side skin and hinge shim, should these not be dimpled? If so, when do we dimple these?

Dimple the flange right before you rivet that top skin on. (I asked Vans about this very flange dimpling question too as it's not specifically mentioned when to do it). I would suggest you not rivet that skin until you install your electrics and avionics as you lose a lot of easy access.

Thanks for the confirmation.