the unequal pipe thing may have been to broaden the power band by peaking the cylinders at slightly different rpm
like tuning ignition, exhaust, and intake 500 rpm apart. they don't give you the highest peak but it spreads out more
dunno how vibration would be affected
leo goff told me to use 1 5/8-inch pipes. i have some standard TT pipes to experiment with, 1 3/4-inch and whatever their length should be. i think the length was pretty much stadardized by years of flattrackers.