Never owned a set and never plan to. I have a set of Doug's in the box but am probably using the factory manifolds. TTI is too proud of something they blame the assembly of the car on in regards to fit. My advice is keep working your tooling until it not a problem or don't make someone give up their birthrite for a set of headers they may have to work over to make fit. JMHO and it's just a general statement...
It is not wrong of TTI or any other header manufacturer to require the engine sit in the OE location. After all, they designed the headers to fit that way so how would they be responsible for mods that change that?