[Darrin Wright]

Dale,
the back rest section of armour has 4 holes, 1/2" dia and they sit inside the cut-out to access the air cleaner. I am not at home to access & measure mine (but checked on the weekend). Pic attached.

479-3, from memory as I have just made them, 1/4" thick (or 6mm), 1 1/4"to 1 1/2" wide and the length is long enough to fit between the 2 lower locating tabs welded to the centre bulkhead. Where this plate engages with the tabs, there should be ground a chamfer (on the forward edge) to accommodate. The upper/top part of this bracket has a curved radius at each end. There are a series of holes, countersunk for the wood screws that secure this bracket to the wooden backrest.

The wooden backrest was made from hardwood, horse hair and leatherette. I think 12-19mm ply should do the trick with hi-density foam.