Those are the LS pads. I got them by mistake for my 83 non-LS bike and had to send them back.
Yes, the shorter one has to go to the top. The cam is assymetric and it can't work properly the other way up.
Mine (the right ones this time) aren't a great fit in the drum, although there was a small ridge (~1mm) on the extreme outside. I ground it off and smoothed it like I would with an old car - force of habit. They usually stop the drum coming off if you have self-adjusters. So my drum is partially worn.
When the back wheel is off again, I'll run a rasp over the worn 'high' points to see if I can get more contact. A small SLS drum is never going to be 'impressive'. My friend tells me the police reduced the width of the rear drum on the 100s as officers found it too sharp??? I suppose size 12 Patrol boots probably meant a 'stomp' not a 'tiptoe feelie'
P.S. These drums are 200mm. 250 on LS. The front drum on my old XT500 was 150mm. Puney! It was swapped for a bigger twin leading shoe from a Triumph, with some spokes missed-out. I paid a guy in Nottingham to do that, as I can only just tweak a bicycle wheel straight. He could also straighten fork tubes with a pair of V blocks and a sledgie. I mean, roll on glass to check straight.
