After looking around on internet and reading a couple of threads here I decided I could make a basic trailer hitch for less than buying one.
First stop was Kenny U-Pull where I pulled a hitch off a Mazda mini van. It had tabs that bolted to the bumper and end plates that were bolted to the bumper mounting struts.

I forgot to take a picture before cutting it up, but this is approximately what it looked like.



I cut off the end plates and modified them to mount them on the rear of the car as supports and attachment points. Here is my mock-up of the hitch with approximate placing of the end plate / supports.



I marked and drilled 2 holes in the bumper, using those holes I mounted the hitch temporarily so I could mark where to drill holes in the rear of the trunk.

I had to take the bumper off to drill the holes (including one of the bumper holes because the exhaust was in the way). I installed my 2 supports, loosely and reinstalled the bumper. Next the hitch was bolted to the bumper and to the supports, and then I tightened the four nuts in the trunk.
I don’t like drilling holes in my 924S, but there are only six of them and it is for a good cause.

Here is the inside of the trunk.



And the hitch all bolted up (next job is to clean it up and paint it).



One of the advantages of this installation is that I can take the hitch off by undoing four bolts and sliding it off the supports (which stay on the car, and make reinstalling easy because the hitch slides onto them while installing the bolts in the bumper, so you don’t have to hold the weight of the hitch during the process).

I returned to Kenny U-Pull and was able to find the wiring for a trailer including the converter to go from European brake/turn signals to North American trailer wiring.

Total cost less than $40 and a couple of hours of work (trailer hitch $27, $10 for nuts and bolts, $3 for the wiring connection).

And this is why I went to all this trouble.

 

Good idea and well executed, we need a pic when it's painted and towing that cart!

 

This thread is not just to allow me to show off my project, but to offer an other alternative to those who want to add a hitch to their car. An advantage of my hitch is that there is no welding involved, all you need is a metal saw and a drill.

For the wiring I used these piggy-back connectors so that I didn’t have to mess up the wiring with those ugly quick splice terminals.




Unfortunately several of the original female bayonet connectors were too loose or broke when I removed and tried to reinstall them, so I had to install non-standard replacements. Something to check if you have tail light problems?

Here we are finally at the track. Mine was the coolest tow vehicle in the paddock! Under the hatch I had lots of room for my tools, starter and battery, spare bits and pieces, helmet and suit... and a spare engine (for the kart not the 924S ) For those who are interested, the kart is a mid 1990s Tony Kart with a Vortex 100cc JICA engine mounted, the spare engine is a similar CRG JICA.

 

Sweet!!

 

Just to finish up... here is the hitch removed and painted. You can see the supports that remain on the car just under the bumper, hardly noticeable from a normal viewing angle unless you are looking for them.