Well done Mat for keeping us going.
The Mat Gaskets were OK in my opinion but as far as I could see were single use.
If we ever get stuck I can supply 86mm od x 75mm id x 1mm in copper. I don't think copper would be a problem as it was used for head gaskets in years gone by. You could use a little instant gasket on these if you thought it was really necessary.
I only mention the copper gaskets just in case anything goes wrong availability from the people above who have invested time and money in this project.
Kindly, Paul