Are you suggesting that's not a common thing to do? It's worked for me and I know I'm not the only one who's done it. There is a factory mandrel made specifically for doing this so it can't be that uncommon. I can't even remember what I used to do it last time, but I know for a fact that it wasn't anything even resembling the right tool for the job. No harm done. What specifically are you concerned about? It may not be the "right" way to do it, but it would save wasting an otherwise good pair of head gaskets.