I've seen the arguments and tested it for myself, and yes, it seems that the new drain mechanic in SR4A for Direct Combat spells encourages overcasting. To try and limit this, and to bring the drain for overcasting in line with the drain from not overcasting and getting a lot of hits, I propose the following: keep the Direct Combat system the way it is. However, if you overcast a spell, add (Force - Magic)/2, rounded up, to the Drain DV. This way, a Force 6 stunbolt cast by a magician with Magic 6 with 6 net hits used for DV would be 8S drain, and a Force 12 stunbolt cast by the same magician with 0 net hits used for DV would be 9P drain. Basically, the overcast spell would get the job done, but would be much more dangerous to the caster.
Comments?