If you want some under bonnet storage that is waterproof, dustproof, makes good use of the space, doesn't involve a lot of fabrication and has storage pockets to arrange things, check out a bicycle trunk bag. This one is a Topeak MTX and looks like it is almost made to fit under the bonnet, it even tappers down at one end. It has velcro attachment straps that can be used if you want to make it easily removable.

The pipe from the oil tank is because I was changing the oil when I took the photo.



[Linked Image]