Is it humanly possible to change the MTU of the ethernet card (le?) with
NetBSD 1.4.1 (hp300)?   ifconfig doesn't work (and the man page says
that many network interfaces don't support changing the MTU).

Background:

 I've got a RH linux firewall that speaks to the outside world via a
 pppoe (PPP over Ethernet) ADSL connection.  The MTU on that
 device is 1452.  The firewall in question also speaks to my internal
 lan using another network card (mtu 1500).  My NetBSD 1.4.1
 box is on that network (mtu 1500) along with another Linux box (mtu 1500)

 My problem: ipchains doesn't seem to handle the mixed MTUs very
 well (or I've misconfigured them).  So I changed my internal network to
 use an MTU of 1400 and everything works fine.  Except I can't change
 the MTU of the hp300.

 Running OpenBSD on the hp300 works fine.