That piece is pretty important. It is supposed to keep the backrest from bending the rear bracket backwards. When I put on my backrest, it came with one rear bracket. When, I bought the luggage rack that you bolt oto the backrest, it came with another, more beefy rear bracket.

I often have 60+lbs on my luggage rack in addition to the OL leaning on the backrest. I certainly wouldn't want to try getting by without those flat straps that tie the front to the back.

 

I left mine off, as well. It has not been an issue, yet. I saved it, just in case. BTW, I am over 300 lbs, leaning up against my wife who is not thin. And still, no issues.

 

You had better spank those parts people the kit is supposed to be complete.

 

I was told they are no longer included the straps in the doscking hardware. It is now only included in the sissy bar upright. My dealer had a couple of them in stock. They were less than $10 bucks iirc. You'll probably be ok for the weekend, but I would get them eventually. Especially if you are going to have a luggage rack with gear on it.