You mean has anyone ever fitted a straight piece of pipe into the exhaust instead of the middle box?

No I doubt it.
 
got paddocks version on mine camer back box aswell bigger bore think it was £34+vat and delvery
 
I lost the back box when I did a side exit exhaust and it sounded fine. When I lost the centre box too it was just too much. Now got a cherry bomb centre box.
 

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