I kinda have one 0.040" Cometic. Let me explain. Last year sometime I bought two 0.060" Cometics. I didn't want to run 0.060 and the price was the same regardless of the thickness (as I recall). So I took the rivets out of the 0.060s and pulled out a shim (they're 0.010) and a bossed end layer (also 0.010). Taking two 0.060s apart like that left me two ends and two shims that will make a 0.040 gasket. (I essentially got three 0.040 gaskets for the price of two this way.)
So...if you were planning to take them apart and spray in between layers, I would think this would be fine for you. Heck, it even saves you the trouble of having to drill out the rivets since I've already done that. In reality it doesn't matter anyway. The rivets do nothing, so you can just put the sandwich back together and run them the way Cometic recommends.
Now I never did run the car with the Cometics I did install. I hylomar sprayed the two 0.040s I made for my engine and installed them. I chickened out though after all the horror stories I read on Cometics. I pulled the heads and took them off before I ever even put the engine back in the car; let alone fire it up.
If you don't mind "re"using Cometics, I can sell you the whole allotment which would be:
2 unused shims
2 unused end layers
4 sprayed and installed, but never run shims
4 sprayed and installed, but never run end layers
Let me know if this is as clear as mud
and if you're interested. I can also take a picture of the whole gang so you can see what I'm talking about.
BTW, I ended up using hot air steel shim gaskets.
Mike