First off, Hylafax and USR modems aren't a 'great' combination. That said,
I ran a similar setup for some time with the same firmware as you are
using. My results were best when running the modems in Class 2.0 with
rtscts (hardware) flow control. You appear to be configured for Class 1
with xonxoff (software) flow control. Again, it probably won't be perfect,
but making that change helped my functionality (and got rid of a bunch of
EOP errors like you're describing). Re-run faxaddmodem, select class 2.0
and type 'rtscts' when it asks you for flow control.