I can vouch for the rear shelf not being beefy enough... I have 6 3/4" Blaupunkts in mine right now (75w RMS per channel), and unless you're listening to distant FM stations or light classical music, the bass flaps the shelf, making it sound like there's a blown speaker. I'm thinking about just laying some fiberglass to the underside of it for stiffness.

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1981 300SD - Sunburn Gold, 200ish k.
1984 300D Turbo "The Green Lantern" - Mango Green (DD) - 183k with no more fingers to count on
1979 300SD "The Whale" - Black (Back-up mega-sled, soon to be for sale!) - 160k and no longer keeping track...
Confucius say: Man who run behind car get exhausted, man who run in front of car get tired.