[PSIG]

If you are after cubes, then I'd suggest just get a simpler-building 289/302/351. Not worth the extra expense and wasting block life boring metal out to get 8% more cubes. If you're into the 221, you're not into raw power, or much of it anyway, without power adders. That's not the point of the 221. Plus, as it's only recognizable as a "SBF", and not a flathead or something distinctive, it's grouped right along with those others by onlookers. They can't see those few extra cubes, so... It's not impressive, it's just cool. Do your thing.