Thanks Smash.
All the brackets were removed from the bracing strut (but still in place in this photo), none of them apart from the steering support are needed. We also heavily trimmed the mounting brackets where they attach just in front of the doors.
If you were doing one dashboard you could probably cut it about and get it to fit, as we were doing two we decided to make the dash sacrificial and then when it was right take a mould.
The dash is only held on by the 3 screws at the front of the dash. The screen demister vents that sit on the heater box are very solid and almost hod the dash on its own. The centre front bulkhead panel has been made lager and after many goes is a very tight exact fit. The combination of the 3 screws, vent mounts and the bulkhead panel make the whole dash very rigid. We have also removed the steering column section, to use the original tou have to remove the stalks which is a pain, you wouldn't want to do it twice. We are using the existing BMW steering cowl covers. Looks very neat and not so bulky.
can see from the picture how complicated the wiring is. All the lugs on the support bar have been removed. You can see the 2 vents that supply air to the screen. We were going to cap the centre vent which used to supply air to the face vents but decided against it as it would probably interfere with the flap as it a couple of inches above the rim. The demister vents should be very effective, the other 2 settings, face and cabin will just vent behind the dash. The is a 4" gap all along the back lower edge so the cabin should still warm up nicely.