Firstly, What version of Redhat 9 are you running. From information I got from elo just prior to release was that the driver was built for US boxed sets only. I had a international boxed set which used a newer kernel and had a few fixes:
http://rhn.redhat.com/errata/RHSA-2003-135.html. I am now back in comunication with someone from elo to see if we can resolve the issue but it could take some time.
Secondly in response to "Is it possible to run a setserial command before linux installs?" I am not sure what you mean by install. For my setup with the old driver I had to create a /etc/rc.d/rc.local file which had the following lines of code (from memory:
setserial /dev/ttyS2 irq 10 #setup touch screen on com 3
setserial /dev/ttyS3 irq 11 #give com 4 its own irq
Let me know how you go. I have yet to try the new drivers since release. I was considering trying Madrake 9.1 early next month to avoid the problem with requiring a US boxed set.