Ipfilter 4.1.13 and freebsd 6.1

[Nicholas von Waltsleben]

I am currently running a couple of 6.1 and 5.4 servers as firewall /
routers for my company.  I am experiencing some problems on the 6.1
server with ipfilter where it blocks oow (out of window) packets.  I
have tried to update to the latest version of ipfilter but was unable to
compile my kernel after running the kupgrade script in the ipf source
folder.  Does anyone have any hacks / patches that they have used to get
ipfilter version 4.1.13 running on FreeBSD 6.1-Release?
 
Regards,
Nicholas