The Filink file set of the V5.21E are:

• UD80-DRV.COM  (UD-80+ PX-8 driver version 4.2)
• WSX.COM (Portable WordStar driver for the PX-8 version 2.3)

The Filink file set of the V7.11c are:

• IRM.COM Integrated Resource Manager version 2.7 for the PX-8)
• PIN-DRV.COM (UD-80++ driver version 1.8p)
• WSX.COM (Portable WordStar driver for the PX-8 version 3.1)

This suggests V5.21E is intendend for the PX-8 and V7.11c is for the PX-4. The two WSX.COM files are different, which is then expected. But the IRM.COM will not run on a PX-4, as it complains it needs a newer OS-ROM, M25030CB. But this ROM is for the PX-8, not the PX-4. The IRM.COM needs 25 pages of User-BIOS. Text in the file refers to the DS-8.

AFAIK, there is no Portable WordStar for the PX-4. The internal version numbers are different, so both are mostlikely for the PX-8.

The PIN-DRV.COM seems to execute without error on the PX-4 (assuming 4 User-BIOS pages), but does not reroute the console to the UD-80. 'Pine' is the internal name for the PX-4 board. The PX-8 is 'Maple'.

(The 7.11c version is a patch from the original 7.11A, so it works with the Re-UD-80. Otherwise they are identical. the bytes changed are the EF9345 register setting, the banner text and the checksum)