Hi Jeremi
We checked with the RAE (The Royal Academy of the Spanish language) and they give an example where cualesquiera is used in front of a noun too. As cualesquiera is hardly used nowadays it is difficult to find sources referring to this, but if you want to share some of the sources you found confirming the only acceptable position is after the noun, please do share, so we can look into it and double check.
Saludos
Inma