I haven't used one for years either. The last time was for an ammonia refrigeration system. For some reason the refrigeration engineers/vendor spec'd them. Part of the reason was to keep slag from getting into the equipment, especially on the suction lines. But on all of the other ammonia systems that i did, we'd usually just tig the root.
If i remember correctly, we ran 7018 all the way out. I don't really have any tips other than run a little hotter than normal, and pay attention to the sides to make sure you get a good tie-in. The extra heat helps this. It's easy to get lack of fusion, especially with 7018 if you're running too cool or too fast.
You shouldn't have any problems really, overall i think they're easier than open root since it's almost like having a backing plate/tape.
Good luck on your test and let us know how it works out for you.
