Sure don't knock using tape for the runs, its is effective, virtually all aerobytes sessions I ever read have taped on ammendments to the cars for testing, although they test up to 80mph so anything that develops force needs to be well attached for what could be 180mph in your case.
Rear spoiler I was thinking something a little more DIY do you have a spare boot lid?
W.r.t. the bonnet there are many ways to do this and were not talking F1 level of prep - we want a join or sorts between the top of the arch liner and a vent in a similar position on the bonnet. Vent wise you could buy something preformed and cut a hole in the bonnet to fit it - mark out the outline of the vent in bonnet in masking tape and pen, use a good HSS steel drill, pilot hole 3mm, then use a bigger drill or a step drill to open up to say 10mm, then you can use a HSS jigsaw blade to cut out the shape. Remove the tape and stick the vent to the bonnet top surface using 'serious' stuff adhesive. The vent is an exhaust vent not a scoop.
You will then need some hose or tube going through a hole in the arch liner in a position towards the inner part of the arch (hole saw, jigsaw, heat with a heat gun and use new stanely blades to cut which ever option you feel will work) the hose ideally will connect to the vent but there is small issue of opening the bonnet, thus you may want a more rigid tube which then meets the vent on bonnet closure. We aren't talking air tight, but more or less working on the principle that air will follw the pressure gradiaent from the high pressure arch to the low pressure air flowing over the mid bonnet line.
You may wish to test the 'solution' after doing one side, some tufts of wool or string taped round the vent opening will tell you the air direction, if they are sucked into the vent then this is a failure, bad luck, but if they stand off the vent then its doing its job, its a 2 man test with a volunteer to stick their head out of the window and see what happening say at 50mph (I suggest doing the passenger side first
).
This is my idea, heres to links to items I would consider for the job
vent -
http://www.merlinmotorsport.co.uk/p6902/BLACK-SIDE-AIR-SCOOP-INLET/OUTLET/product_info.html run so the narrow end is near the windscreen
hose - http://www.merlinmotorsport.co.uk/p4227/63MM-RED-SINGLE-LAYER-DUCTING-(PER-METRE)/product_info.html need maybe 2m to play with some shrink joiners or jubilee or some gaffaer tape works well.
Not teaching anyone to suck eggs but some tools I would use
drill bits -
http://www.screwfix.com/p/dewalt-extreme-2-hss-drill-bit-set-13pcs/66597 Step drill -
http://www.screwfix.com/p/step-drill-4-22mm/15976jigsaw blades -
http://www.screwfix.com/p/starrett-metal-cutting-50-x-4-5mm-24tpi-jigsaw-blades-pack-of-5/39966 need a jigsaw of course. You could use an angles grinder with cutting discs but that a really rough way of making a hole.
Hole saw for the arch liner -
http://www.screwfix.com/p/titan-downlighter-holesaw-set-9pcs/71760serious stuff glue -
http://www.screwfix.com/p/evo-stik-serious-stuff-adhesive-290ml/23941what are we emulating here, well this is a high end example
of the dtm car arch venting
http://fi.wikipedia.org/wiki/Tiedosto:Audi_A4_DTM_2006_vr_EMS.jpg
ond on the rear of the N24, I think you can see a way you could do it.
http://www.reverie.ltd.uk/astonmartin_archventing_modification.phpI wouldnt fit any after market 'styling' kit as thats all they are, the only wind tunnel tested item for sure would be the std.
List of things
1. Tape shut lines - easy, simple
2. Tape radiator opening unused SMIC inlet - easy
3. Flatten the bottom of the car - not so easy but would reduce drag decently.
4. Make a front lip, air dam, or splitter - not so easy must be well held on. lower the car as much as you can.
5. Vent arches
6. Add tail strip to boot - easily done, stip of ally, some rivets and some serious stuff. like this but with less angle -http://www.hotrod.com/techarticles/body/hdrp_0609_aero_tricks_tips/photo_09.html
These are not costmetic improvements, thus you may prefer some second hand bumpers to adjust then convert back to nicely painted items after the day. If you have spare doors gut them, cut out the inned frame, cut out the impact bars (8inch cutting disc on a grinder is how I did mine - Sparco did his also), remove the window motor, and retain glass in the best wedged in bit of wood to the bottom of the door you can way!, cut the excess strengthening out of the bonnet, do the same to boot (dont cut the hinges off).
I think you really could win if the engine is up to it.