The 1783-NATR's NAT table is limited to 32 entries according to the documentation.
There are a lot of other NAT's out there with more features at a better price if you're not married to the AB name. No affiliation, but here is one I've used in the past with good results:
https://www.ccontrols.com/ctrlink/eipr.php
Certainly more cost effective!
Nice thing about the 1783-NATR is that the routing table can be displayed in the PLC's memory image when the NAT is declared in the I/O tree. I didn't look deep but I wonder if the Skorpion can do the same.