Re Sabatti double rifles, are they actually regulated the traditional way at all? Or is the job attempted by using a cheaper less reliable method? ie the reason we are all seeing reports of why some rifles shoot well, and others have problems?

Jeff give some good advice above. Especially the bit of asking for effectively (my words) a money back guarantee the barrels are not crossing and are properly regulated when making a purchase.

There are always trade offs for lower prices on DRs, especially re regulation as it is a time consuming and expensive process.