I have a Bestem T-929 also and had to shorten the bolts and (the way I did it anyway) also cut off the supplied brackets at an angle to get it to seat on the stock luggage rack. But, it's on, it's stable, it's capacious and was way cheaper than any other top case option I could find... And it shipped immediately, when I got my Glee the Givi cases were on 4+ weeks backorder and I just couldn't wait that long!
Here's my T-929 in action, as I tested its capacity for a 4-day road trip I'm beginning tomorrow.
(1) I needed it to fit my duffel bag of clothes, etc., in the trunk with my sneakers placed on top. I packed my duffel bag a bit loose to have "squish room" for the sneakers, and the trunk lid shuts easily.
(2) While parked, I plan to put my riding gear in the trunk. If I'm sightseeing or something I'll lock the duffel bag with a thread lock while putting it on my seat, if I'm off the bike for the night I'll take the duffel bag with me.
Here's a 4-pic montage of the T-929 with first my Joe Rocket Super Street boots, then my FirstGear Mesh-Tex Overpants, then my FirstGear mesh jacket. It all squishes down to close the lid. I have to wiggle it a bit to open it up again but I rehearsed it 2-3 times so I don't think it's something that will get stuck on me unexpectedly.