Paul,
Agree with the plan on getting rear of bonnet to align and then drill the mounting holes. McGregor sells the Rear Cowl Seal as it is known for BE's. McGregor is in CA. Look in the back of Classic Auto Sport classifieds for an address and phone #. They sell rubber and gaskets for LBC's that actually fit.
I used some draw latch brackets from McMaster Carr. SS and adjustable mount with 2 screws each and hold up to 400 lbs. load. You may want to think about using these until you get final positioning, curve in the bonnet, etc. You need a way to totally secure the rear of the bonnet, clamped properly in place, and then drill front mounting holes for the forward tilt brackets. Once all is aligned and set up then install the Dzus Type fasteners.
Like the Play-Doh trick, not sure if those rubber fender bumpers are really needed. I know my bonnet is too low in the front and a long term project is to redrill/somehow raise the front to get proper rear alignment. Not much a 1/4" in he front translates into a big movement at the rear. My issue is I've rounded out / elongated holes in front as much as I can really go. Solution is rear clamped down, front bolts removed and use a n adjustable jack or some other method to slowly and accurately raise the bonnet front so all is in alignment, then drill permanent holes. My bonnet works great, I just need to slightly tweak alignment issues to make it better. Unfortunately the alignment piece is a 2 person job and I haven't been able to convince the wife to help hold the bonnet up while I redrill holes. One of those will do it when I get "roundtoit" things.
I love the front tilt bonnet, so much easier to access everything and the look of the forward tilt bonnet really draws lots of questions at car shows. Keep at it and you'll get things fitting right.