Be mindful that a mod like DudleyAZ's is about the only way of getting good results, with a center stick.
Meaning an extension of the base, not the stick tube!

I remember helping Kimchoc with a mod of his Saitek stick. He tried adding a curved tube to the stick and extending it way above the base. There were two major problems with it.
1. The springs designed for a joystick are WAY too weak to support the weight of the extension.
2. Extending the stick means proportionally increasing the stick "stir". You'll end up banging into everything!

As a concession, he ended up drastically shortening the extension and building a platform, between his legs, to mount the base to.
It was better... but a base extension, with a stick like the Warthog (that has a small base footprint) would be the best course IMHO!

Unless you've got the big bucks, for an off the shelf center stick.

That's what I did. If the stick base was much lower, it would hit my legs when moved about the roll axis.

Another thing that you need to consider is the distance from the back of the seat to the stick - the distance needs to be comfortable even when the stick is fully forward (so you aren't leaning forward off the back rest). I ended up cutting into the seat base (also from a car), and setting the stick base about 120 mm closer than the seat previously allowed. Alternatively, use a seat that has a short base.

Grizzly and Julian are dead on. When I modded my Cougar, I tried to floor mount it, and both issues came into play. I ended up replacing and augmenting the springs, and that only partially fixed the sloppy stick issue. It would take a full rework of the entire spring assembly to completely overcome this problem.

The stick stir deflection issue also played into it. Side to side wasn't too bad, but front to back was a real problem. With the Warthog, you have just enough height to the round base it comes on to get the stick above your legs, alleviating the need for an extension, although it wouldn't be hard to do say a 6"-8" one if you wanted. Anything longer than that and you will start to run into all of the issues.

Here is what mine ended up looking like installed.
Dud