[skyking]

Thanks again. I think shooting automotive would be easier ,once you have it primed.
I had not looked closely at the foamular products.
That C-300 you used may only have half the compressive strength at 30 psi, but it has equal the flexural strength at 75 psi.
It looks like a better choice. Flexural strength is more about the rigidity and I would not be surprised if it had comparable shear strength.
That's the one weak point of the common EPS and XPS foams, internal shear.
To get excellent shear performance you have to go to very costly marine materials.
I'll have to check on local availability of the C-300.