Technically, he's right. It does change the geometry. However, I question whether it's a SERIOUS effect. "Throws off the whole geometry" sounds a little severe, but I can understand why he says that. It there's a problem, it's on him.

With the very limited travel most street rods have, I don't see a problem. This is not just conjecture. I shortend the upper A-arms on my '30 A-bone by an inch, and moved the lower ones inboard an inch. I saw NO problem with steering, no bump steer, no wandering, no effect at all. Interstate, city streets, drag strip (at 119 mph) . . . drove like a go-kart.