Except (and correct me if I'm wrong) my understanding, based on the Magic Resistance examples on pp. 85-86, whether Ulrich uses Rego to pick up a chunk of wood, move it over to the magus, and go bambino upside his head or whether he picks it up and hurls it at him, either way it has to penetrate. The example bridging pages 85 and 86, about a "normal rock thrown by magic stops at her skin or clothes" seems to indicate that either way, he has to get a pretty hefty Penetration.
Now, if he were to move a block of wood over the magus's head and let go, then Magic Resistance is irrelevant (Aiming, p. 86), but he would have to make an aiming roll for that, too.