Actually never mind, just saw FDev posted some specs. So maybe, 100t difference.
IIRC, it was reeeaaaalllly marginal, squeezing a C5 prismatic shield onto a Cutter.
Will it cope with 100t of extra mass?
True story:- I did actually roll mod's for a 5A prismatic shield for a Cutter, ran it for a while but then decided I wanted a bigger shield more than I needed an extra 32t of cargo capacity so I upgraded to a 6A prismatic and sold the 5A.

.... and then FDev introduced Guardian Shield Boosters.
Objectively, I suspect I would have used-up at least 32t of cargo capacity fitting GSBs with the 5A shield so the 6A wasn't a terrible decision but selling the 5A was a dumb move.