How to use named pipe with hashcat?

I'm trying to use princeprocessor with mask together. While I can get princeprocessor work alone with normal pipe, I can't make it work with named pipe as it seems I can't do stdin with mask. As soon as hashcat reads the pipe, princeprocessor stops working immediately. I read and tried what the Practical PRINCE: 1 CPU + 24 hours = 63% Linkedin hashes cracked, 100% automated post wrote, named pipe without mask and it failed like the previous.

$ princeprocessor < words_alpha.txt | hashcat -m 10900 -w4 10900.hash

Doesn't work:
$ mkfifo fifo
$ princeprocessor -o fifo < words_alpha.txt
$ hashcat -m 10900 -w4 10900.hash fifo

what I want to accomplish:
$ hashcat -a 6 -m 10900 -w4 10900.hash fifo ?u?d?s

Can anyone give me some advice on solving it? Thank you.
the problem with named pipes is that they act like a normal file, but have no "file size", so hashcat will read through all of the input to discover the number of password candidates (or "length") and can't really seek back (that's not allowed with named pipes)..

you could use other techniques like appending with rules etc
Thanks for the advice. I generated the needed rule with maskprocessor thus eliminated the need of named pipe. Still, I wish hashcat can take it as input.