I too have the same setup. Pioneer on top of the double DIN installation in a '94 Toyota 2WD PU. I also mounted the Pioneer directly to the OEM bracket and drilled two sets of holes on either side to mount the sled w/four screws/nuts.

One note of caution: Even with the low clearance heads do check that the holes you add to the sled won't interfere with the drive mount screws (the ones on the side of the empeg). I didn't check this, the first time--I only checked to make sure it would clear as the chassis slid in--and it did slide in. It went in with a nice solid CA-CHUNCK right past those dang screws. But then I couldn't get it out. There was no way I could pull the chassis out of the sled by hand. I finally ended up (he hides his head in shame...) a crowbar to "convince" my player to leave the sled. All ended up well. I shaved the heads down with the dremel and it goes in(and out) smooth as silk now.

Best regards,
Tim
(I've also done the same install on a friends Saturn which has worked equally as well.)