Redpower sub blocks and spawning?

[ba12348]

I run a small server for a friend and myself, and we recently decided to colonize the nether. All is going well (quantum suits make this too easy) except we still have a pigmen problem in our building. The floor is a layer of construction foam, with a platform of the redpower cover blocks, both smoothstone and cobblestone, and we still have an issue with pigmen spawning. Logic would dictate that these are non-solid blocks and the pigmen shouldn't be able to spawn, does the game recognize them as solid?

Pictures:

Interdiction torches were to separate the area I had put panels on from the solid floor, there was also a magma cube when I went to take this picture, but it tried to kill me.

P.S. since this is my first post here, do the Technic forums not have a

code?

[PieLover]

I've got a feeling it all comes down to the way you placed the covers on the top half of the bottom wall layer, instead of the bottom half of layer two (hope you understood that). This gives the pigmen a perfectly stable platform to spawn on.

[ba12348]

Hmm, I wondered about that, The goal was to make a floor that couldn't be spawned on, but was otherwise unnoticeable. I'm going to try replacing the slab layer with glass blocks, and either paint the CF below, or lower that by 1 block and do the slab design between it and the glass.