OK,
after searching a bit harder it seems I may have been on the right sort of lines with my updating of xorg.conf.
can I just use the xorg.conf and xorg.conf.pluto.avwizardr that works on 0710 and copy them over the ones on 0810?
when I have had a go at changing xorg.conf before I have just replace the modline in the current xorg to the one I though matched as per
http://forums.whirlpool.net.au/forum-replies-archive.cfm/1203126.htmlat 1360x768 but I would rather go with 1280x1024 as that seem to be best on 0710
and then it seems I need to
"in the admin web site, go to advanced, config, devices, choose core, the core/hybrid, on-screen orbiter and update the PK_Size and Screen Width / Height values to match whatever resolution you forced in."
to get the orbiter going at the right size
and then it should work, right?