An ongoing programme to replace all the nasty corroding zinc plated screws on my Elise with stainless steel ones. The table below shows all the ones I've found to date. You'll also need some washers to match; I haven't itemised these so get a selection of M5 and M6 standard and 'penny' types and use whatever seems best. 

Note 1: There are several different types of stainless steel, and several are NOT suitable for stressed applications, so unless you're really sure you know what you are doing, then leave your engine mountings, suspension bolts etc. alone.

Note 2: Sigh. I have learned that aluminium suffers from electrolytic corrosion when in contact with stainless steel in a damp or salty environment. This means that the fixings for the rear undertray should be dipped in grease before inserting, and insulated by means of plastic washers under the screw heads. I don't yet have a solution for the front undertray fixings as these screw into aluminium retainers. This does not affect the wheelarch liner fixings, as they use brass threads.

Part	Position	Thread	Length	Quantity
Rear Diffuser	Rear edge	M5	15	5
Engine Undertray [1]	Rear edge	M5	15	5
	Side	M5	15	3 per side
Front Undertray	Front edge	M5	15	3
	Rear & sides	M6	20	9
Rear Wheelarch Liner	Front	M6	20	2 per side
	Rear (to clam)	M5	20	2 per side
	By exhaust (locknut)	M6	20	1 per side
	By electrical connector	M6	20	1 per side
Front Wheelarch Liner	Front edge (to clam)	M5	20	2 per side
	Rear	M6	20	3 per side
Blanking Plug	Rear edge of door, by latch	M5	10	1 per side
Side Window Frames	Underside of door	M5	20	4 per side (2 pairs each)
Relay block	Top of NS wheelarch liner (access through front bonnet)	M5	20	2
Fuse box	Top of NS wheelarch liner (access through front bonnet)	M5	45	2
Number Plate Lamps		Self tap	8	4
Rear Fog/Reversing Light Grilles	Top edge	M5	20	4 (2 per grille)

[1] These may already have been done as part of the 'A' service.