I've got a build thread going over in the fuel injection forum:
http://shoptalkforums.net/viewtopic.php?f=23&t=128778
My plan is to do efi and learn the basics of fuel and ignition control using megasquirt, and then eventually add a turbo on the car.
I've looked at the hideaway headers, and like the way they get everything out of the engine compartment, but some have had turbo drain issues, and your pretty limited on space with your actual turbo. I like the idea of your setup, but running the exhaust would be the hardest part. It also looks like my German plenum would push the turbo over to the left side of the engine compartment a little more making the exhaust that much more difficult. The nice thing about your set-up is being able to retain my perfectly good header with the exhaust pipe routed up the turbine, and turbo drain issues are non existent.
I want something that will let me keep the decklid, but I don't have any issues with having to run stand-offs. I've thought the same idea of running the exhaust out the side of the car between the decklid and the body, but I think I want something a little more subtle over all.