Here's the deal. TEC have a batch of r/h mufflers with the mount incorrectly located, over and out. I know they say to loosen the header pipe but you're not realistically going to cheat 6-8mm that way and not have the r/h side horribly loaded up. I've fitted literally dozens of exhaust systems and some leave a lot to be desired with regards to fit. Termis being some of the worst. A good system should go together smoothly and all the mounts line up easily with the system loose. There should be no reason the lever and ratchet strap anything. Sure some mounts may be at one end of the slotted mount hole and need a little juggling when tightening up the whole system but nothing drastic. The Akra system on my 1198 is by a long way the best fitting system I've ever done, fits absolutely perfectly and each sliding joint is a very neat fit, amazing really.
TEC talk about production tolerances in their video but that's why the muffler mount hole is slotted, to compensate for those tolerances. What your image is showing is un acceptable. Personally I'd be sending it back OR possibly taking 6-8 mm off the end of the header pipe so it fits, depending on how much overlap the header to muffler joint has.
Ciao