A silly bug has reared its ugly head. Apparently, our dimension
validations are predicated on JSON parsing order, that is not good. 

So, this commit adjusts the dim validations so that it is an actual
validation, instead of something that occurs during parsing.

Additionally, I found that our custom formats were not overriding
`getMaxDimensions` correctly. Typically, and in production, this isn't
that big of a deal, but I have found it useful to do this for other
testing purposes (so that we don't have to rely on the perfield codec
for more direct and advanced testing).