WL RSB & Cusco RSB reinforcing mounts install Q

[bigBADbenny]

I spent the afternoon in my latest favorite spot: under the Lib!
Swapped out the stock RSB for a WL 22mm adjustable item and Cusco RSB reinforcing mounts. (thanks again Gambit )
I took (alot of) extra time to encase the RSB mount bushes with MTB innner tube so as to help keep the bushing greasy, not squeaky...

My question is about the Cusco RSB reinforcing mounts: is there a third bolt (not supplied) that goes through the uppermost hole and if so, are there any suggested bolt/washer /nut combinations recommended?

Here's a pic that might describe what I'm inquiring about:

Nothing in the upper hole, the corresponding hole on the chassis is enormous!
So for now the RSB is on the "soft" setting so the car is unlikely to explode, at east for a week or so.
Any advice most appreciated. Link to the other pics here.

[Kekotic]

[bigBADbenny]

Thanks, mate!
Do you remember what the washer arrangement was like at the back of that upper nut?
On my wagon, the chassis hole there is ovoid and about twice the width of the corresponding hole in the Cusco mount...
I guess a short bolt and a stack of big to small washers will do the trick...

[bigBADbenny]

After a little Googling I did find the answer!
Now to measure and make a pair of those square washers...