Here some basics. Big pipes for top end. Small diameter pipes for low to mid range. The crossover is to slow or neutralize the pulse on that 90 degree crank on the 1-4 is helping from cleaning too much out of the overlap. Suck out too much and the fresh charge in is being sucked out too. So it is a fine line of test after test you getting the muffler or that suck back in, (timed right). It's all about timing for that pod or stock air cleaner on the carb side. The less bends on the pipe, the sooner the charge leaves from that exhaust port.

You go from stock air box to pods, then that will throw the pipe off you made for that new setup. You dramatically changed the speed flow. So every minor or major change is going to make some effect. The crossover will not matter too much where it is. You would have to make so many pipes and dyno that change.

If say the crossover is a hassle you can work the muffler hitting the atmosphere instead. You want that grunt for economy and max HP, so small header pipes it is. Pass on the crossover if a muffler helps keeps the cops from pulling you over. Instead of burning your hand, start with a cold engine and feel the pulse you are working with. Say you hold your hand over the muffler hole and feel that suck back in the pipe. Or take a rag, place it over the pipe's exit and watch the rag get momentarily sucked in the hole. That reversion is the spent moving back into the chamber to mix with the fresh incoming air/fuel. Once the overlap sends that movement going, there is an opposite reaction, meaning the pulse in reverse.

You refill that chamber with that pulse back in. Your goal is to time the spent back into the chamber. When the exhaust valve closes, you should have a cunt hair of spent (reversion) back in when the exhaust closes and all the fresh charge ready to fire off... You made the perfect pipe for that engine combo. It wouldn't work on another bike and pull the same HP numbers is my guess.