Right, turned out the Saab unit did indeed seal on the bottom with a rather complex rubber seal that sealed off the outer and inner sleave.
No matter how I mounted this: with little or a lot pre-load or with or without silicon sealing added, it would fail instantly pressure was put on it.
I have never removed and mounted the engine block so often this last week.
After 6 or so failed attempts, I binned the Saab TOB and ordered 3 others (I am pressed for time as a trackday (Bilsterberg, Germany) is in less then 2 weeks) which looked low enough form their pictures online.
One is a Ford Transit unit, the other two are SsangYoung and Deawoo units.
The Deawoo unit is actually great, but its diameter for the (G50) pinion axle (1.0 inch) is just a tad too small (24,0mm).
The Ssangyoung unit fits the diameter but its base is too wide for my adapter plate. Both seem low enough though!
The Ford Transit unit however is lowest of all, fits all around and only has a weird line feed (press-fit?), but I think/hope that M12x1,0mm thread can be cut into the arm at a lower position.
Ordered the M12x1,0 taps, so fingers crossed it all works and solves the problem I had..
