If anyone is interested, I finally got my Samsung 7000 series TV to be automatically recognised, with pause and FF/FR to work without having to manually set Twonky to PS3.
I am using both a CHLv2 and a XHL, The mods are slightly different for each but basically the same.
First you need access to the root of the NAS. This means telnet in and login as root. You must reset the password, and there are many forums around on that.
I upgraded my firmware using shonk's excellent firmware mod from over at Buffalo Nas-Central (http://forum.buffalo.nas-central.org/viewtopic.php?f=68&t=23603)
If you follow the instructions (reset to default) after updating to this firmware, it does several very nice things, including resetting the root password.
I had no trouble with either the CHLv2 or the XHL.
The object of telnetting in is to modify the 'clients.db' that Twonky uses for DLNA.
Once you find this file, make a backup (with the telnet cp command) and modify the original file.
It is located (from the NAS root) in
CHLv2 - /usr/local/twonky/resources/clients.db (Twonky 4)
XHL - /usr/local/twonky-alt/resources/clients.db (Twonky 5) (case sensitive)
Useful links
Telnet commands - http://kb.blackcoralgroup.net/kblore/article.php?id=071
vi commands (telnet editing) - http://www.cs.colostate.edu/helpdocs/vi.html
If you open up clients.db with vi and scroll up and down the file, it is obvious how the formatting is done.
You can modify one of the current clients in the file, or add a new one, just follow the same formatting as the file.
Twonky V4 format is slightly different than V5, but the info below is the same.
Add (or modify) the follow.
NA:Samgsung TV
DD:Samsung DTV
XM:DLNA15
XM:FORCE_DURATION
XM:FORCE_4TH_FIELD
XM:AARES
DL:MP4DLNA
DX:SAMGSUNGFEATLIST
DB:FIX
MT:mkv video/x-mkv
MT:mpeg,mpeg2,vdr,spts,tp,ts video/mpeg
MT:avi,divx video/avi
HP:chunked
The mods above are a combination of the latest clients.db from Twonky (that didn't work) and experimentation with the PS3 settings
The key to getting the Samsung to pause and FF/FR was the line DL:MP4DLNA
Anyhow, this worked for me, and I looked high and low for a way to do it without any luck.
Best of luck, Oh! I will not be responsible if you 'brick' your unit.