typically the aft end of the pipe is fixed with a former so you can't adjust it much so you're left with adjusting it via the front mounting tabs. some pipes have long tabs and can be adjusted quiet a bit others not so much. as far as mounting the turbine, the jet should already have mounting rails that set the centerline of the turbine then just match the front of the pipe to it and you're good in most cases. if you have it offset it'll hot spot the pipe and if off enough it'll burn a hole in it. also if you mount the turbine too far forward your pipe may come up short, you also don't want it too far aft or the pipe hangs out the back too much (looks bad)