[David Hodgson]

NASSTY
I myself have been hesitant to use gas struts, as even in the closed position they still exert force onto the boot/ bonnet which could potentially warp boot/bonnet surface over time.

However if you still choose to do so I would suggest that you attach a bracket to the boot hinge mounting screws so it is acting close to a point that cannot be easily warped, same for the bonnet, an attachment on the hinge itself would be ideal but that leaves it restricted for a forward mounting point for the strut.

Most auto parts shops have a range of struts in stock of varying lenth and strengh for various cars, that you could rumage through, also tractors use shorter and lighter ones on their windows and hatches etc.