You need 1 eva foam floor mat, 60 cm X 60 cm, 1,5 cm thick.
Step 1: CUT
Cut the biggest circle possible, it is a very nice size. I read somewhere the shield was supposed to have 76 cm diameter, it is just 16 cm difference and I am not very tall, so it suits me well.
Step 2: Mould
This is a parabolic dish, it will be used as mold.
Step 3: Heating
After appying heat to the foam with a heat gun (several times each side of the piece), put the circle on the dish, apply some weight and leave there for a while.
Step 4: Shape
Now it has the shape, but it will need hardening.
Step 5: Back Straps
Now for the straps. I used bended plastic flanges to hold the straps and eva foam.
Step 6: Hardening
For the hardening: first 3-5 layers of white glue with sanding between them.
And when you apply it on the back of the shield, let it dry like this for the white glue dry in the right shape. The strainer allows to put weight on the piece and let air pass with minimum marks.
Now some layers of Smooth-Cast 65D and, after each one, a nice sanding.
Step 7: Carving and First Layer of Paint
Step 8: Finish Painting and Battle Damage Look.
Step 9: Ta Daaaaa!!!
Very light and totally safe.