"Rear Hump" *Installation*???

Howdy folks, I got an odd one for ya.

A friend of mine picked up a Spec Miata that had a Kirkey in it, mounted pretty much directly to the floor (using welded-in vertical tabs at the very rear of the floor).

Previous owner removed the "rear humps" to do so.

This is a problem, as that Kirkey does not work _at all_ for my friend.

We'd like to go back to a more stock layout, like the PCI Racing offerings.

But you'll note that they're designed to mount to rear humps that...aren't there.

What would *you* do, dear reader?

So far I've come up with designing a rectangular pyramidal/trapezoidal "block" or "spacer" that can be fabbed out of...whatever...go under the bracket, get welded in (I believe Spec Miata/the SCCA require all welded-in components use a surface area of 6"+), then drilled/tapped accordingly for a bolt to go through.

Any better ideas/suggestions/recommendations?

We'd really like/prefer to go a route for offering usage of more stock-supporting brackets.

Thank you, all!

Find someone who builds roll cages, and have them fab up whatever you need. Probably costs not much more than buying off-the-shelf for a basic 4-point rollbar anyhow, and it will be the fit/design you want. 

I'd just weld in whatever block of whatever is needed to mount the seat mount. Without looking at it I'd guess a pieces of 1 x 2 0.120 wall tubing would do it.

You can bend the tabs on the PCI mount so it's not necessary to get the angle exactly the same as original floor.