Regarding the chippers for the HF (and other dado sets) not leaving
a flat-bottomed groove: It may be the saw. On mine, the threaded
portion of the arbor is *ever so slightly* smaller in diameter than the
spot where the normal blade seats. So I sometimes have trouble
with the bottoms of dados cut with a stacked set.
I can tell it's the arbor, because the first blade goes onto its seat
with essentially no perceptible play whatsoever. The chippers,
and outside blade, which sit on the threaded portion of the arbor,
have a barely perceptible play when I'm putting them on. Swapping
them one at a time for the inner blade proves the problem is the
arbor, not the holes in the chippers and outside blade.
I suppose I could pull the arbor, and either have somebody make
a new one, or weld some metal onto this one and re-machine, but
so far, I've been able to live with it.