I am not sure I understood - are you attaching to the quadrant or adding a small tiller? in both cases the Raymarine Type 1 requires a radius of 250mm. The throw for the type1 is 300mm end to end.
By the way, there was a point where I though of attaching to the quadrant, but I discarded this idea - can't remember now if it was due to tight space for installation, problematic angles, or another reason.
Attached is the installation manual, which may help you plan the installation.
As for the setup - if memory serves me right it is not "changing" the 4000 to 5000 - the firmware is simply identical, and as far as I remember I just followed the setup procedure as it appears in the ST5000 manual (attached), and it was a simple matter of changing it from "wheel" to "tiller" or something like that. It should be in the "dealer setup" section. I suggest you look into your unit before deciding since this possibility is firmware dependent. My boat is 2004 and the firmware was OK.