OK I promised a feedback but as I cant find Nelson cookers in my local chandlers this is probably a waste of time.
Summary:
Original cooker 500mm wide
Nelson Spinflo 450 mm wide
Packing brackets made, see photos
Gimbals won't lock, when cooker door opened the bottom swings forward and there is a risk of anything on the hob spilling.
Numerous emails to Nelson resulted in the unpublished figure of 455mm required between the mounting brackets.
Shimmed packing brackets
Gimbals still won't lock. Really cant see how they could. The cooker is just about an interference fit between the mounting brackets but minimal friction. Why would you want friction? The cooker would slowly wear away. The mounting brackets are far too thick to distort inwards so even turning the ridiculous eared locks as tight as you dare does nothing.
Made a a packer to fit a bolt at the bottom as per the Techimpex and cut down a shoot bolt to 30mm. Drilled into the side of the cooker.
Now it locks.
Challenged Nelson to film a 10 second video of a Spinflo locked in place but er, um, not sure we can do that.
They are now info@thetford-spinflo.eu, so that's THETFORD SPINFLO NELSON which I hope makes this show up in any future searches.
New/old cooker photos here:
https://www.flickr.com/gp/139059806@N03/2705h5Previous reported problems from just one forum:
https://www.flickr.com/gp/139059806@N03/WzG463