The breeding that will reveal if cinnamon and black pastel are variants of the same gene or are allelic would be to breed a cinnamon/Black Pastel (super) to a normal. The resulting offspring should show the same pattern that you seen when you breed a mojave/lesser (BEL super) to a normal (that is, you will get normals, mojaves, lessers, and BELs from the Mojave/Lesser BEL X Normal breeding).

If cinnamon and black pastel were the same gene, this breeding would produce 100% black pastel/cinnamon-looking animals which should be an intergrade between the two morphs. If cinnamon and black pastel are allelic, then this breeding would produce normals, cinnamons, and black pastels which will all be distinct from one another.

Since it's been widely stated that cinnamon and black pastel are allelic, I have to assume that this breeding has already been done.

So, it's not a matter of opinion at all--it's either one or the other, genetically, and will be definitive when proven (if it hasn't been already).