I altered this a bit - let me know if it rings any bells immediately (going for the state dependent memory trick here) the plate is a little less than 3 mm the silvery section underneath the bracket is 2mm
and thank you!!! The spacer is two sections of pipe JB welded together. The silvery part is actually rather thin walled so I built it up with JB weld too
This looks like a good job, my only advice would be to try and match it to the single available high quality photo from the exhibition to get it just right, even if it contradicts the measurements I gave.
BTW, check this video out:
https://www.youtube.com/watch?v=X1cWj6q_bZ8
should give you an idea of some of the weird stuff in this exhibition. 10% real props, 40% very badly made fake props, 50% fan art (including a twi-lek nude painting)
Also pause on the macrobinoculars, might be useful?
The exhibition featured in the press a lot, but I have been too lazy to search the Japanese internet much more yet (where the good press pics came from)
google/twitter/youtube
スター・ウォーズ展
スターウォーズ展
and
スターウォーズビジョン
to see if you can dig anything else up! (all of those say star wars visions)