The hold down strap should be like this:https://andover-norton.co.uk/en/shop-de ... p-p11-p11a
but it needs the clips or pins on the ends and will attach to your battery box floor plate hooks. Check "Post Photos of your Norton P11"
in this p11 section and check out P400's build. 2nd picture down I think the terminals are facing inboard. I haven't got that far on my build yet. If others respond then I will even learn something to your good question
On Any Sunday...A motorcycle is what ever you want to make it. Turn it on, and you can give yourself a real thrill...