The following will not answer your question, but does offer some background on ShareCenter compatibility. D-Link stated that the filesystem between the DNS-323 and DNS-325 has changed, rendering RAID configurations incompatible between the two series. Standard Volumes, however, were assumed to be swappable between the two models. This information predates the release of the DNS-345, which based on your observations during testing, may have undergone further filesystem revision.
Even if you successfully get a DNS-345 formatted HDD to mount in your DNS-325, do you really want to trust storing your data on a HDD that wasn't natively formatted on the ShareCenter model it was intended for?