After 7 prototypes made in wood I now have a bracket made in 10mm 7072 alu.  I designed it using eMachine shop in 3D but had to convert it into 2d .dfx file for the water cutting guys to be happy.
The job was done by a local machine shop and cost me a fortune.
The bracket before milling. Straight from the water jet cutter:


I'm sure 7-8mm would have been adequate but 10mm won't hurt when the Rotrex will put 20+ hp of force on the 6-rib belt.

I later did some additional machining on a simple milling machine I have access to:

I used my PS pump as a bracket but had to cut it in half to fit the compressor section of the C38.  See my other post for my trunk mounted MR2 EHPS conversion. The upper bracket is actually a modified PS bracket. I'll cut off some more metal and paint it black once everything is aligned and verified.  It also serves as as support for the auto tensioner.
The spacers are 25mm alu made in a lathe.

Here is a early pic fitted to the engine with the Rotrex, autotensioner and adjustment pulley. I have later milled out 25mm holes to make the fugly 17mm bolts flush with the bracket.  I would have used M10 umbraco bolts but it is impossible to find M10-hex in 1.25 metric threads anywhere in Norway. I found a place on the web but they wouldn't ship outside of the US...

The small pulley is a Miata cam belt pulley and the tensioner is a Gates 38178. I need to space out the pulley on the tensioner to align correct with the belt.
The Rotrex pulley is an 80mm 8-rib but I will use a 6-rib belt with a 6-rib 145mm crank pulley from FM that fits my ATI-damper. I believe the belt is 1170mm .

I designed the bracket to be compatible with AC but removed it due to problems fabbing up a new tensioner for the AC belt. That and getting rid of the condenser. 3- layers of heat exchanges is enough. If I knew I would run without AC I would have tried to mount the rotrex lower down where the AC was located .

Todo:
- hotside IC piping with BOV and WG
- Intake/filter
- Rotrex oiling system

The plan is to have things spinning and pumping air into the engine in april.