Are the "properly degreed" lift blocks supposed to be something to stay clear of as well?
I was under the impression that a high quality block which has a locating pin, proper bevel or "degree" to retain correct pinion angle would be acceptable and keep costs down as opposed to replacing your springs. I would avoid the homemade blocks on anything that sees any highway use at all. Trail rigs or mud only rigs can get away with less liability.
I am probably willing to draw the line at about the 4-5 inch mark. I'd say your right on the money for six inch and bigger lifts.