Hi Chuck - Most contractor saws and hybrids will just barely accept a full stack, and typically need to leave off the arbor washer to do it...which is a common practice recommended by many manufacturers. Most cabinet saws have slightly longer arbors and will accept the stack with the washer.
I have not tried the Grizzly dado, but did read some solid positive comments from a forum regular who owned it....can't recall who or what forum!
The design is similar to the Systimatic 42T/6T Superfine dado set that I had....that was an excellent set, but with a retail of $300 it sure the heck better be!
Oshlun has a similar set too that's nearly an identical design to the Systimatic that's getting good remarks as a very good dado and excellent value. (I believe
Holbren offers 10% to members...?)
If you're uncertain about trying the Griz or Oshlun, Grizzly has the
DW7670/H7200 set on sale for
$89.95, which is more money but is a really nice set with a great case and very nice shim stock, and it's more proven.
As far as flat bottoms go....
truly flat bottoms will only come from an flat top grind with excellent precision....I'm not aware of any sets that use all FTG teeth on the cutters (doesn't mean they don't exist), except for the box joint blades, which are limited to 1/4" and 3/8". Most dado sets use an ATB because it has lower tearout, but leave minor "bat ears" at the bottom of the kerf. Some alternate an FTG raker to minimize them. Tearout on the backside is a partly a function of the grind, the hook angle, number of teeth, feedrate, the material, etc., etc....using a backerboard can minimize that a lot. Oversizing the piece, then ripping to final width after the dado cut will remove the tearout (as long as you cut off the exit side!
) If you want "good" to "very good" performance, a $50-$100 set will probably do the trick. If you want top shelf performance from a dado set, you're probably gonna need to spend $150-$200 (Infinity, SD508, Ridge Carbide, Forrest). A router bit is one method of getting a truly flat bottom dado cheaply, but the tearout is usually worse than with a dado set.