OK ... I investigated further ...
You can select the TH resolutions in the "Video Setup" by clicking "Show all resolutions" tick box.
Once you choose the TH resolution the Setup Box becomes too big for the screen and the various choices for entering the game ... setup etc. are off the bottom of the screen.
So it looks like it isn't possible to get into the game ... but ...
If you change the size of this box using the resize tools (top right) you can make the box much smaller ... BUT ...
this must be done before you change the resolution.
Once you change the resolution the box appears to be too big again ... but ...
You can get it the right size by choosing "Online Arena" which you
can still see ... then without inputting anything choose "Cancel" ... this takes you back to the Setup Box which is now resized to fit the screen ... :)
All of the above is a right fiddle faddle ... and I was having problems trying to work it out as each of the boxes keep resizing themselves ...
So I made the ... clip.cfg ... read only and this seems to fix the box at the right size for TripleHead ...
Once in the game there are various view to choose from ...
The cockpit view is a bit too zoomed in even when you zoom out to the maximum ... you can look around in the cockpit to see the controls but it is a bit of a pain.
The other views look fine and you can use the zoom in and out feature but the FOV is not altered with the resolution and so the view is chopped off at the top and bottom ... :(
I can't find a way to increase the FOV correctly.
I do think it is playable though that as long as you are happy to fly around in the exterior view or when in the Cockpit view you are happy that in order to see the controls you will need to use keys to look around.
Some screenshots ...
As you can see the width FOV is no wider ... and so the top and bottom of the view is cut off ... :(
4:3 Cockpit view fully zoomed out ...
TH Cockpit view fully zoomed out ...
4:3 Exterior view fully zoomed out ...
TH Exterior view fully zoomed out ...