This was enormously easy and quick, and has a lot of potential - but needs a lot of work as written.
1. The filling was bland bland bland. Next time, I will use fresh garlic and quite a bit more herbs. Some peperoncino, too, probably. (These would probably also be great with a ricotta-and-egg-and-herb filling, though that would have to be piped into the tubes with a pastry bag.)
2. There wasn't nearly enough sauce, and I used a full 25 ounce jar. The second layer of tubes were still way above al dente, and I cooked it at pressure for 12 minutes. Next time, 2 full jars of sauce (make sure the sauce comes at least 1/2 way up the sides of the SECOND layer of pasta).
3. Note that most commercial pastas sell these as "manicotti" (in Italy, manicotti are made from crepes, rolled around a filling, while cannelloni are stuffed pasta). They generally come 14 to a box; this amount of filling can fill all 14.
4. Don't over-stuff the pasta tubes; the meat needs a little room to expand, or it will either squeeze out the ends or burst the tube.