So, I know that the ability to limit a share's reported free space has been a request for a while, and I know it is unlikely.  I wonder, however, if it would be possible to create a vdisk or similar disk image, stored on the parity array, and mount IT as a share?  This would them present anything accessing it as only having the space the image has - so applications that limit their disk use to available space would still obey that limitation.  I just don't know for sure if this is readily possible on unraid.

Shares have a setting to limit reported size for timemachine. I wonder how that works and if it can be used for smb in general