Sorry, cudaman, but you are wrong, no BS... the name "flat tappet" is a misnomer anyway. There is about a 30 inch radius on the curvature, pretty much impossible to see with the naked eye over a .904" diameter, but it is there.

The usual test is to put two lifter bottoms together and they should rock, since they are both convex. That will also let you see the gap as you rock them.