Would making a shaped insert that slides inside the current 300 flanges and can be rotated for adjustment be feasible? Drilling a small hole and a tapping in a grub screw to stop it rotating around once it has been aligned with the ports would be easy enough. Only problem I can see is I recall there being a weld inside the 300 flanges, though this could also be worked around.

Just throwing an idea out there, as it would save someone having to modify their exhausts.
_________________
MC21 Honda NSR250. TYGA 300 conversion.