Hi Sylvain
I am not sure if I have understood your post fully.
Most builds will use 2 universal joints to form the steering shaft. ( Unless using the original Ford rubber damper at the steering rack )
Here is a photo of AshG's steering shaft components before he welded the extension bar in place.
Such a set up should not need any additional support for the shaft.
One UJ is being held fixed rigid by the bulkhead bush & the other UJ is being held rigid by the steering rack.
This type of set up should allow for an angle but is not likely to be floppy.
If you were to make your shaft as you have pictured a couple of posts back, you would almost certainly need to provide an additional supporting point for the shaft.
Hope this makes some sense.
Ps
Sorry to AshG for stealing his picture.