I have found a method of prepping the slot that receives the sail tabs. I don’t know why I didn’t think of this sooner. Before attempting to insert the tabs into their slots, I take a small file and carefully clean and ever so slightly enlarge these slots. Since I have started to perform this operation I have not broken another sail tab.
Some of the tabs seem a bit too short and there isn’t enough of the tab inserted in the slot to hold the mast securely. In this case I put a drop of cyanoacrylate glue on the bottom of the piece that received the tabs. Cyanoacrylate can also be used to tabs that might have gotten a bit too much pressure inserting them into their slots. This can be avoided by using my fist method filing.