another jungle souljah - good to know. long live congo natty.
are you prepared to cut metal for this? if so the trick is to remove the metal you'll need to allow your drivers to fire through the shelf, re-fit your blind trim piece, draw lines from inside the boot on the back of the trim piece and then cut them out, leaving the blind mechanism intact of course. now you have holes in your trim, stretch and glue a couple of layers of tights over them (this prevents tell-tale sagging) and then re-cover the whole shelf with acoustic carpet and trim adhesive, voila you have an acoustically transparent shelf that completely hides your install from the outside world.
as for installing your speakers, you're going to require a baffle to hold them nice and solidly. 18mm mdf is the go - cut a piece to match the underside of your shelf area. roofing bolts drilled down from the inside of the cabin will bolt it all up and allow your shelf to be re-fitted without fouling their heads as they are very shallow. as for the gaps between your baffle and curvy e30 shelf, some glass fibre and/or expanding foam work will seal them up. if you masking tape up your entire shelf and baffle then suirt expanding foam into the cavities and let it go off you can then pull them away and have perfect shaped void fillers. these can either be used as is or as templates to re-create in fibre-glass, preferable but more work.
as for doing away with your bootlid torsion bars see
gas strut mod for bootlid link
do you have these 8 inchers already? i think you'd be better off with some rear fill speakers, components if possible and a sub or even better 2! trust me, it's what i run and jungle proper kicks in there!
hth - paul
yeh mid life crises probably 
