i just did it for that speedster. i grafted SC extensions onto 73 bumpers and filled the middle with a section of a front long hood bumper. took a bit of cutting, reshaping and welding to get the 73 bumpers to blend into the SC extensions. the car had a 3.0 turbo engine and a monty muffler, so the lower skirt had to be more vertical than usual to cover the muffler and incorporate a heat shield so the paint wouldn't peel off from the heat.

I was running yellowbird bumpers on my SC. But I wasn't settled on the front so I put the standard front bumpers back on and modified the rear to be a Yellowbird/impact bumper hybrid. So ruf bumper, valance and lower quarters but with bellows back on.

I've not seen anyone else do this and I'm pleased with how it turned out:

https://farm6.staticflickr.com/5494/...75115a0c_b.jpg

https://farm8.staticflickr.com/7445/...425cc8e9_b.jpg

https://farm6.staticflickr.com/5528/...049e73eb_b.jpg

https://farm8.staticflickr.com/7391/...9549d9f3_b.jpg

Sounds like you want some weep holes on the underside of the bumper where no one can see it, right?

I've seen a slot on the top on the bumper where it meets the center reflector, read that it allows a lot of heat to escape. In addition this is exactly where some people have had paint blistering.

I'm no longer drawing on paper or using my photo program (not photoshop), taken to drawing right on the vehicle.

My next step will be clear tape and cardboard for full scale modeling mock-up.

I think the version on the left looks best with the rubber trim on and no built-up upper lip.

The version on the right is best without the rubber trim and with the top lip (per earlier studies).

Porsche Custom Photos by kach22i | Photobucket
http://i184.photobucket.com/albums/x...ps95fb1aa2.jpg
http://i184.photobucket.com/albums/x...ps4862f08a.jpg
http://i184.photobucket.com/albums/x...psb4ccb81b.jpg
http://i184.photobucket.com/albums/x...ps09943a6e.jpg
http://i184.photobucket.com/albums/x...psd3189bfe.jpg
http://i184.photobucket.com/albums/x...psceaae610.jpg
http://i184.photobucket.com/albums/x...ps1e4c7cb9.jpg
http://i184.photobucket.com/albums/x...psea2103b8.jpg
http://i184.photobucket.com/albums/x...ps2567b723.jpg


It came out great, I'd try to copy it but I'm afraid I'd fall short because of my current skill level in fabrication.

I'm starting to like the dynamics and visual flow of the right side.

http://i184.photobucket.com/albums/x...ps55065545.jpg

I really do have to mock in that upper lip to get the flow right. Some updated studies below.

2B
http://i184.photobucket.com/albums/x...psf99f9abb.jpg

2C
http://i184.photobucket.com/albums/x...ps32d656f8.jpg

2D
http://i184.photobucket.com/albums/x...ps94343733.jpg

Some more minor variations and studies of other designs.

2E
http://i184.photobucket.com/albums/x...ps45093b4d.jpg

http://i184.photobucket.com/albums/x...ps017b0c91.jpg

I did some cardboard mock-ups today, along with re-positioning the license plate.

http://i184.photobucket.com/albums/x...ps44b9fc28.jpg
http://i184.photobucket.com/albums/x...ps91e20038.jpg
http://i184.photobucket.com/albums/x...ps8a74850b.jpg
http://i184.photobucket.com/albums/x...ps61888553.jpg
http://i184.photobucket.com/albums/x...psb668007d.jpg

http://i184.photobucket.com/albums/x...ps0cd72380.jpg

http://i184.photobucket.com/albums/x...psd51bd162.jpg

The photo immediately above shows the possibility of tucking in the bumper about 1-1/2 inches, and also removing an equal amount of material from the top and bottom flanges of the bumper which meet the body.

EDIT: Below is what I'm favoring now.

http://s184.photobucket.com/user/kach22i/library/Porsche%20Custom
http://i184.photobucket.com/albums/x...psefaa660d.jpg

I think you should take the bumper off, as well as the rear fender quarter panels. Start over, but forget about re-using the old stuff. Otherwise, you're not really doing a design study, you're just tweaking the existing stuff. Maybe you can make the rear of the car sweep up into a rear diffuser, and offer a glimpse of the underside of the car through air vents, or something original to these cars?

I'm fine with just tweaking it, and it plays into future plans I have for the exhaust (going to freak some people out perhaps). Even a modified stock bumper is going to offer more protection than a fiberglass one, which is one reason choosing for this direction.

The lower rear valance is pretty rough, a few dings and possibly bend in the middle, it's hard to tell. In either case it's going to get modified as well, just have not shown it yet to keep things simple.

I'll be taking off much of the rear to work on it, including new light weight rear crush tubes made of aluminum (and shorter).

I've taken just over 100 lbs off the car so far, but the next 100 lbs is going to cost me a little money, as little as possible is the goal.

The top lip of the bumper is going to be a solid stock of aluminum ground down to fit, it may need to take a few nudges from idiots in parking lots. Yet another reason to trim off and cut out as much as possible elsewhere. The early sketch showing an angle with concealed plate lighting is out for now.