The 12a engine in that car is NOT a stressed member - in the photo of the engine you can see the tubes linking the rear bulkhead to the transaxel adapter. - (iirc) Formula Atlantics don't use their normal TOYOTA engines as a stressed member either.

 

Here are some pics that Buzz asked me to scan in for him...

 

Thanks for that Craig.... gee lucky your nickname wasn't already taken!

Although my photography sucks, these show the layout of the whole deal. It does use a sump plate, but its not like the plate alone is akin to a chassis. Despite his workshop having some good links with Mazda Motorsport Australia (eg... they build race engines and did racecar prep for the factory team in Targa Tasmania and production car racing)... they couldn't get any hard data on how to use the engine as a stressed member... so they just went out and tried. The engine sits between to BIG chunks of alloy billet, adapting the trans onto the rear, and mating the engine (minus front cover) to the bulkhead behind the driver.

The car was at the launch of the RX8 for local dealers and somone looked at the ralt and announced it couldn't work... so apparently the owner ripped into some tire smoking helis / donuts and then left it idling saying something like "well, it did that and it's still running.... next question?"