If you have room to put on another washer and the bolt hole for the large top bolt will allow the movement then go ahead and put in another washer. If not that then I suspect the only solution is stronger bars. Can't tell from the picture but you may be getting receiver wind up which means the receiver is twisting, or even possibly the shank is moving upwards slightly because of sloppy fit, which will reduce the amount of lift the bars can provide at any given chain link.
By the way, you can run with the bars on the 8th link and the bars slanted up just fine as long as the chains don't hit anything or pull the snap-up brackets during turns. I doubt that will happen since you have 8 links under tension which will allow plenty of movement. I would continue just as it is for now and see how it does.
Barney