Ok so I was off by 1/4" on the 11-14 exhaust size.. As for not having any reason behind the Solo system not fitting, I've been corresponding with the CEO of Solo Performance via e-mail regarding the fitment for the 05-10 models in which his exact response was, Solo Performance does not offer exhaust kits for the older 2005-10 3v cars at this time.. He also stated that if I were interested in a Solo exhaust system, he recommends that I take my car up to their facilities and have their shop custom fabricate an exhaust kit that will properly fit my 2006 GT.. Therefore if the 11-14 kits can be adapted to fit with a couple of adapters as you stated in your post, then why wasn't this suggested as a possible alternative by the CEO of Solo Performance
Edit: just got off the phone with Rich who's one of the installers from Solo Performance.. Anyhow he did confirm their 2011-14 exhaust systems will NOT fit on the older 2005-10 cars without major modifications.. His reasons, the exhaust hangers are in different locations and he also mentioned areas such as the size/shape and bends of the OTA pipes at the rear axle are also different and would more than likely not clear over the rear axle.. Therefore he strongly recommends taking my car up to their facilities and have them weld in a pair of J-pipes either towards the location of the gas tank or further upstream towards the H crossover section in order to provide adequate clearance for best fitment.. At any rate, it appears that I'll be following Rich's recommendation by having Solo fabricate and custom install J-pipes onto my existing exhaust setup, rather than go through all the hassle and added expense by having a shop do custom fabrication mods to the Solo exhaust systems designed specifically for the 2011-14 S197 models..