Dear Mat,
please find attached the photos we did on the lead mask. The work has not yet been finished but 
photos are useful to understand the problem.
As you can see in image n. 18, our technician constructed the lead mask point by point and
 he told us that he is able to reproduce it with an uncertainty not less than 1.5 mm.
He told also that he would be able to reproduce the 4 masks with a less uncertainty 
drawing an arch in place of the single points on the lead brick. So, we were discussing
 if you consider reliable to fit all the theoretical points of the profile with a curve
 and reproduce the curve on the lead brick.
Please, for any clarification and (in case) for a better discussion, 
contact us at the number +39 06 30484873.

                Greetings

                 Angelica