Thank you and thanks for the paperWelcome to K20a.org mrluke!
Amazing what can be done out of digital pictures. I am interested in the quality. Did you measure the bolt pattern in the model and compare it to the real bell mouth bolt pattern?
A very good basis for your design approach is this paper here: RET_Bellmouth_Sept.pdf (profblairandassociates.com)
The accuracy is really very good, you're talking about fractions of a mm really. The biggest issue is my photo quality isn't great so the software struggles to find the edges of the dark grey object against the slightly darker grey background. I scaled the model to an overall length of 250mm and checked the widest diameter across the trumpets, 64.6mm in the model and 64.6mm in real life.
The picture below shows my model and the cad scan overlayed so you can see the differences
As you can see its mostly around the edges with little pockets on the surface finish. I think I may have more success using a green screen as the background rather than black so will try that in the future.
And here's the model looking slightly prettier. Renders aren't my forte, I just make and print the parts lol.
There's a bit more work to do before its a finished part, the edges need tidying up so that it looks smooth rather than faceted. But for a couple of hours in CAD i'm pretty happy with where I have got to.
I'm not going to spend much more effort on this design because I don't want/need to print trumpets that duplicate the originals. This is good enough to get the dimensional accuracy, next step is to create an elliptical profile in both stock height and shortened lengths.