I've been setting up the mic about a foot away from the grill to let the sound develop a little, starting pointing at the outer edge of the cone (this takes 3 people by the way) While I monitor in a seperate room (preferably with someone else to help me listen for the spot) I have the guitar player playing, and someone else with headphones on slowly move the mic stand across the front of the speaker (I mean slow, like an inch per 10 seconds) for one complete pass, just listening for the spot to come and go and where it gets too grainy. Then I have them move it back to the starting point, and do it again. When we hear the spot, I tell them through the headphones to stop. Then I have the guitar player double track a section of a song, pan them out, and have him come in there and listen. If it sounds good, we keep it. If not, we keep moving it until we get it. I've been building a box around the cabinet with fiberglass panels so that no room gets in the mic. I basically lean one against each side of the cabinet, and lay one across the top.
This is the 441 a foot out, boxed in, on a Peavey head with totally shot tubes, using exactly the technique above. See if you like it. It is a tad grainy, but movement of the mic dictates how much or how little grain you get.
www.nowhereradio.com/demoking/singles its the One Fine Line song
Also keep in mind when recording heavy guitars you want to roll the bass out some, turn the gain down a little bit (or a lot) and get some mids back in it. Most guys slam the bass and scoop the mids, gain on 9, treble on 10... back it off and look for the tone 1st. Add some mid. Tame the highs and bass. Roll out a LOT of bass. THEN mic it up.
Peace
Paul