I've cut quite a few of these Hondaline trim plates for riders who wanted my Highlighter to fit either a Mustang or Cobra backrest pad, which is shorter than the Honda pad. Generally, Honda chrome is pretty good - only a small percent peel, like under 10%. You cannot tell if the chrome was improperly applied by inspecting it - One of my platers used to add a throwaway part to go through the baths at the same time - then whack that piece with a hammer - if it blistered, the batch was bad. There are many causes of poorly applied chrome - but that is always the reason if it peels. You can reduce the probability of peeling by cutting with an abrasive wheel rather than a toothed blade. If it's marginal chrome, the blade will always knock it loose. You can use a cutter wheel in an angle grinder, or a chop saw - either work. Have a water bath or spray handy and cool the cut as an abrasive cutter will raise the temp to the nearly-coloring point - and you might cross that point. Don't go slow with the cutter - that will heat the chrome more. Use a belt sander, fine grit not courser than 120, if you have one, to remove the burr, with the belt moving towards the shiny side, perpendicular to the plane of the plate. Best if the belt does not have a platen behind it.
Hmmmmm. Well, I have a good angle grinder, but have never needed to use a cutter wheel. Is that the same as a "Cut off" wheel? And I've always pictured a cut off wheel as being used to cut off nails and such, not to cut metal plates. Trying to picture how to use it with a flat chrome plate. Should I cut on the dull side or chrome side? And I just grind along the line I want to cut, like using a blade?