Just been trying to screw my amp to the rear of the seat. Found either I was hitting some bit where there was a gap (nothing behind the cloth), or most of the screws were not tapping properly. Have been trying smallish wood screws and self tappers (about 1 - 1.5cm long). Which screws are best and is there any trick to getting it right?

Can't you feel where the gaps are before you screw? How much screw thread is remaing after going through the amp?

Yeah. The main thing I'm after is the best screw type/size so they screw in and hold properly, without poking passengers

Can get it so there's no thread remaining - although most of the time, even if it's screwed into a solid bit, it just turns and will pull out. I'm pushing firmly as I screw it in to try ensure the threading takes properly.

Thought of trying sticky backed velcro?

Stuck the rough side of it to the back of my amp, carpet on the back of the octy's seat works well enough as the 'soft' side velcro, not had any bother with it.

I know its not what you asked, but felt so much less hassle than screws when i done it.

Use rivets instead.

I'm not sure the sticky velcro would hold the weight of the amp.

Doing rivets it would probably be more convenient to rivet a carpeted piece of MDF to the back of the seat, and screw the amp to that.

Will probably just screw to top of the sub enclosure like I'd have done anyway had I never read about possibility of vibrations killing amps on the net.

Screwed mine no problems using some small PK self tappers, just drilled uning a 1/8 drill and screwed in.

i drilled small holes then used self tappers

Looks like the key is to drill holes first. Thanks guys, will give another go soon.