underbody brace

[Me]

i jacked up my car today. my car doesnt have the holes in the arrow #6. so i try it on holes #9. it fits perfitly. i am sure it is the front brace. however, the bolts r too small. i need bigger bolts. i tried 11/66 and 17mm wrench on the bolts. it is a little bit loose. any suggestion on finding the right bolts?

[Me]

If you look at the Haynes pic posted by juffa, you will see a pattern of 3 holes (one larger central one with smaller ones on each side) just inboard of the rear lower arm pivot. I have an aftermarket brace bar that is just a piece of steel tube with the ends flattened, and drilled at the spacing between the large holes from one side to the other. They come with a nut that you manoeuver into the channel(bit tricky), and you hold the nut with a spanner under the lower arm inner end. It would be easier to get a piece of ~4mm steel plate that will fit in the channel, but cant turn, drill and tap it (M8?) , slide it into channel, and just screw into it.
jp 92red

I have a front brace from the MX-5 Factory that fits as exactly you described. It uses a plate with two threaded holes that the bolts scew into.

J

is captured nuts the only thing i am missing? how much did u pay for ur install?