On the JMB- the shortest headers have worked the best --simply get the cans as close as possible and use the largest dia header you can get -
ZDZ once set out small headers - the Germans made bigger ones - an improvement!
I went to 30mm id on my 60 --it was even better !
BTW the long bats do not have any peaky character if you get it all correct --on th ZDZ160 -on the 10/80 pipe - a 72cm length from exhaust to band on pipe is good .-nice power and smooth transition -the overall setup tho is preeetty long.
We ran over 6500 on 30x10 Mejzlic way too fast --the30x12 Bambula was at 6100
Youreally should try any setup on a bench before ever putting it in a plane -saves a lot of heatburn.