You won't get the much cross cut out of the garden variety household radial arm saw. I think Dewalt made some long arm models that might come close, or check the Delta Turret arm saws. They might be able to come close (not sure). You can adjust the fence back (maybe) a little, but it won't gain you more than an inch or so. Dado across that much width might be better done with a router and straight edge. Your Craftsman RAS will "rip" cut to 24" (I think), so maybe you could rotate the motor and cut the wood that way. I don't care for the method because of the mess from the dust, but it works as long as you don't have a real aggressive blade (negative hook will work well on plywood in that setup).