Demon 340 exhaust build routes?

I am in process of installing exhaust in my 340 Demon. Up front I have Dougs Headers and I cam off those with a Dougs 3" X pipe. I bought the 2 1/2" custom over the axle tailpipes from Accurate exhaust to go on my chrome tips out the back. I wanted to do the 3" all the way including the mufflers and reducing it to the 2 1/2" on the back of the mufflers. I was wondering what the best way to get the fit good. I am starting at the back with the tip hangers moving forward to the hangers at the rear of the mufflers. Seems the passenger side only needs a small straight interim pipe to go from the muffler front to the Xpipe. The drivers side seems to be cockled a bit on the muffler. Hard to line it all up when it is loose. I did have to get a small reducer for the rear of the muffler to do the 3" to 2 1/2" deal. Should I just start clamping with muffler clamps from the back going forward, so it will sit still for me. Maybe just snug the clamps down to hold things in place as I go? I was originally going to start welding things, but my better judgement feels I may paint myself into an expensive do over corner? HELPEEEEEEEE...
Oh, the motor is a 416 stroker motor, is why I decided on 3" thru the mufflers which are 14" mufflers........