I would suggest building the muffler and leaving the two pipes separate until you can put all three of them against the engine and chassis, so you can work out where each is to sit, exactly.

Dragon's Sd.Kfz. 7 has a similarly stupid exhaust: they mould half of the muffler to the front and the other half to the rear of the pipe, then want you to put them into the chassis subframe separately and then glue them together. Great for painting … not. I cut off the pipe on one side and added a pin there, so I could fit both parts after painting.