It’s the fore end fitting as much as anything that I hate. But I also hate fitting new wood for a fore end so maybe it is me. Sometimes you just get lucky and one fits both barrels. Rare in my experience. It is far simpler to fit or better yet already have the fore end for the second set of barrels. I did make the mistake of trying to use one metal for both barrels and ended up with one who was loose on both. That sucked. Ended up refitting it back to the first barrel and finding a second fore end to fit the second barrels. Measure three times, take just a slight amount I’d metal off and measure/smoke/file or hone slightly.