different materials will bend differently....there's a limit to the bend radius that most machine shops are capable of producing...for automotive applications, space restrictions are usually the determining factor...this is based on the conversation I had with a guy a Barnshaw Bending, up in Manchester....biggest mandrel bending machine in the UK On motorbikes, especially 2 strokes, expansion/contraction and the required angles/shape would be easier to fabricate by using a series of concentric reducers....particularly if it's a one off.
Not ideal but it fits and it's square and level plus the throttle bodies fit ( and they cost me a tenner )
