The mod Savage and Ravage adds a slab and vertical slab that is blast-proof, but that is no longer the case once combined into a double slab.

Hi, thanks for this report! This has been an oversight on my behalf. Currently the mod uses the smallest blast resistance to use as the blast resistance for the block however I believe it is better to use the larger value for this case. I will change this and add this in the next version!

Added this in the latest version!