My impedance curve measurement does not match that of B&C speaker

289cm2 may be slightly on the small side for your driver's displacement.
Going with larger ports with the same Fb won't change the frequency response of the cabinet until pushed to excursion limits when the port may be "blown out".

An undersized port exchanges more heat as it is run hard, so there is some trade off between port compression and power compression.

I probably wouldn't bother changing the ports, but would flare the ends if they are not.
 
  • Like
Reactions: Nicolas225