I began to research the one-piece Driveshaft options.
Utilizing the Search Function on the Subaru based forums I scanned for any information regarding lightweight one-piece Driveshafts.

Amazingly enough, the vast knowledge of the forums fell short.
Luckily though (through some old threads), I found information on a few Companies that offered “bolt on” one-piece Driveshafts for the WRX. Plus, I learned the vast difference in materials that aftermarket performance Driveshafts were constructed from –
Aluminum and Carbon Fiber.

Knowing that I would have to communicate with both manufacturers and vendors directly in order to narrow the search for a lightweight one-piece Driveshaft, I came up with the following List:

Driveshaft Shop - www.thedriveshaftshop.com - One-piece Aluminum construction - 12.6 lbs. claimed weight - Retail price $449.00 - Modification to the floorboard is required for installation

Torqline - www.torqline.com - One-piece Carbon Fiber construction - 10.5 lbs. claimed weight - Retail price $2,950.00 - Modification to the floorboard is required for installation

A.C.P.T. - www.acpt.com - One-piece Carbon Fiber construction - 13.25 lbs. claimed weight  - Retail price $1,250.00 - No modifications required for installation 

Which Driveshaft Would Better Suit my Needs?:  

Needless to say, I was not terribly pleased when I found out that two of the three Driveshafts would require me to modify the STI’s floorboard.

So, what exactly does a floorboard modification mean?
I phoned the two vendors to get the details about the installation requirements and they informed me that I would need to use a Hammer to SMASH my flawless floorboard so that their overly sized shaft design would clear and barely fit into place.
Yeah, right, I thought without saying a word to their representative.

I was concerned, because now I had but one choice, the A.C.P.T. Carbon Fiber one-piece Driveshaft.
But this Driveshaft required ZERO modifications to the floorboard or any other component for installation.

Being prudent though, I did want to do some Due Diligence on A.C.P.T.
before I made the decision to purchase their product.

I found that A.C.P.T. (Advanced Composite Products and Technology) has been making composite components for aerospace, Government agencies, and commercial institutions for over twenty eight years and they have established an outstanding reputation in their industry.
This was good news.

Then I learned that building carbon fiber one piece Driveshafts is a very small part of A.C.P.T.’s business.
In fact, the only reason they even bother to manufacture automotive Driveshafts is because they are car enthusiasts like us.
I was now quite pleased with the research results and felt extremely
comfortable in purchasing their product for the STi.