Well, the guys who did the empeg/amp install just used the bend-outs on the sled to attach it to the trim piece. This meant that the empeg was about cantilevered 3/8" in front of the rest of the panel. (I never got around to taking pictures of this.)
Yesterday me and a dremel spent a few hours with the trim piece, the sled, and the the assembly that's supposed to hold the radio, pocket and cup holder. This assembly is very similar to a single pair of rack-mount ears that hold three pieces of equipment. There are two threaded holes for screws that mated right up to the factory radio and the Sony headunit I put in some years back.
These stock holes would have interfered with the screws in the side of the empeg, so I ended up drilling a single hole on each side of the sled between the inward facing dimples, and matching holes on the "ears". Then I had to grind down the head of the screw that was on the inside of the sled because that was too thick. Even though there's only one screw and nut on each side, it's actually pretty secure since there's not much room to move around, and the back of the sled is resting on pocket below. The lip of the sled is wrapped around a bezel on the pocket.
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One the empeg is in place
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everything is nice, snug, and pretty except for the carnage I had to wreck on the trim piece. The unit is actually slightly tilted, the back is probably about 1/8" lower than the front, which actually compensates a noticible amount for the parallax effect. The surface of the fascia is flush with the a/c panel, which leaves a good amount of clearence for things in the cup holder, which is just below the pocket.
Any suggestions on ways to make "adjustments" to the trim look a little nicer would be appreciated. I was thinking of maybe trying to wrap some electrical tape around the parts I had to grind down, but that would probably look tacky.
The car's a 1995 Nissan 200SX, sort of a two-door version of the Sentra.
--Nathan