I don’t remember exactly when, but 4 or 5 years ago, or maybe longer, Hatco changed to the larger element diameter. If I remember correctly, the first few of the larger style elements we got into stock came with a new mounting plate with an enlarged groove, but only the groove on the mounting plate needs to be larger, the unit frame groove, for want of a better term, did not need to be enlarged. We still have a mixed stock, as an over zealous Parts orderer expected a higher failure rate and set a pretty high inventory number for some of the odd sized ones. I seem to remember that after some length of time, the new elements came in with instruction tags to enlarge the groove on ‘old style’ mounting plates prior to installing. All told, with 80 kitchens/beverage service areas we’ve got 100+ GloRays in our facility ranging from table top fry warmers to full 96″ double-wides. As often as we replace elements over the years I’d have to say yours has served you well to be running into this ‘issue’ so late in the game.