OK, David, I dug out the l/h z-bar rack and sort of held it up next to the '81 garage ornament and these are my assumptions:
1. It looks like there is a hole that will pretty much line up with the shock bolt.
2. It also looks like the hole for the long 6mm bolt at the back of the subframe falls pretty much in the right area. THis is the one that ties both sides together at the back.
3. It appears the front of the mount could be modified to attach somewhere on the ear the passenger peg bolts to. It doesn't fall anywhere close to where it would bolt on a stock setup but I always say, "Where there's a will, there's a way" - provided you have a large hammer and a torch! [smiley=mad.gif]
It looks like the bar will clear the shock and maybe the bag will clear. You'll just have to latch bag and mount together, hold it where it should go, and see what it looks like.
It looked like you should be able to bolt up the rear two mounting points and then you can see where the front/lower one falls before you decide to start cutting and bending stuff. You will not want to bend anything starting from where the bag latch is to the rear. I would think minor tweaking before this point will be OK and it doesn't necessarily need to hook to the stock location.
Oh, my '81 has a mono-shock seat and tail cowl (which ain't supposed to fit) that fits just fine with a little "persuasion".


Click on this one if you have a fast connection:
http://www.suraklyn.com/yabb/pictures/1981%20R100/repaint%20011.jpgHave fun!