81 XJ650 Maxim Luggage rack problem, help please?

I'm the owner of a 1981 Yamaha maxim xj650 and i've been riding it for the last 5 years and really enjoyed it. I recently purchased a luggage rack to attach to it to carry extra items. I got this rack off of ebay and it was labeled as a rack for a 80 xj650 maxim. I checked on the frames and were told they were the same. I can't however seem to figure out how to attach this luggage rack to the frame of my bike. It looks like it's meant to attach to the same clamp as the rear blinkers and then to a forward bolt, but it doesn't seem to be long enough. I would greatly appreciate any help on how to attach this item. Thanks!

 

Might not br for an XJ Maybe XS rack instead. Should mount to rear turn signal mounts and to the forward grab bar mounts (allen bolts) spacers and longer bolts will be needed.

 

I don't think it's an XS rack, i've compared it to other pictures of my bike with it attached and it appears to be the exact same rack. I'm attaching a picture of one below.

 

Are there some "mystery tabs" on the frame under the seat a bit forward of the turn signal mounts? The 550's have them, they're there to mount the luggage rack on. One problem with Yamaha accessories is the "family resemblance" can fool you. 2-point engine guards for the 650's LOOK exactly like the ones for the 550 but they're just slightly larger. You may very well have a rack designed for a different bike. How about taking some measurements and posting maybe someone with a similar rack can help.

 

There are indeed a couple of extra mounting points. From the pic it looks like they would be the front mounting point.

 

The two mounting points on the luggage rack are about 10" apart.