Jim,
That brace is on the top. If you look at the firewall of the stinger, it is not really supported on top, it has plenty of support on three sides only, so I added a brace. It proved to be a good idea.

I may have doubled the gear block, but I don't really remember.
The big thing is the doubling of the side's. When you look at any stinger from the side, without the wing on it, you will see how weak it is at the leading edge of the saddle. I have seen many stingers break at that spot (all size stingers). I ran my doubler from F2 all the way back to the rear of the saddle. I eventually demolished the stinger (really bad) but it never broke there.

Jim