I would like to set the MTU on multiple windows clients.

DHCP has option 26 "Interface MTU", which would appear to be the ideal
way of doing this. However, the windows clients do not seem to
recognise this setting. Checking the current MTU settings with
TCPoptimiser shows that the MTU is still "default" or whatever the
last manual setting was.

Has anybody done this successfully? Is there a better way of achieving
the same goal?

It may be that the windows clients (XP) do not make the request and
therefore are not given the MTU setting. If so, how can this be
changed (although making other changes defeats the purpose
somewhat...). Or it may be that I have entered the data incorrectly -
I have put in 1446; some documents talk about 16bit unsigned integers,
and others 2 fields of octets. What format should it be in?

Config Notes:
NetWare 5.1 SP7
DHCPSRVR v 3.13c