I tried 1-1/2 tsp in a can once, and a few people remarked that it was quite spicy. No one complained, but the fact that people pointed it out made me think that it was a bit much.
I "can" my sauce. Without going into all the steps, I can it into 16-oz jars and put them in the cabinet. Perhaps it's just that I've become used it it and any deviation tastes "wrong", but during the summer, we had a big pizza party (50 pizzas), and used the sauce straight out of the cans (plus the 1 tsp cayenne). Somehow it tasted a little sour or tart to me. I wonder if heating it alters the flavor somewhat.
But I've always felt that pizza is a subjective thing. You might like your Redpack straight from the can, or with THREE tsp of cayenne. Doesn't make either of us wrong.