Splatterpuss,
The issue is not one of rules so much as consequences of rules. This is an extract of FAR 25:
"Sec. 25.777 Cockpit controls.
(a) Each cockpit control must be located to provide convenient operation and to prevent confusion and inadvertent operation.
(b) The direction of movement of cockpit controls must meet the requirements of Sec. 25.779. Wherever practicable, the sense of motion involved in the operation of other controls must correspond to the sense of the effect of the operation upon the airplane or upon the part operated. Controls of a variable nature using a rotary motion must move clockwise from the off position, through an increasing range, to the full on position.
(c) The controls must be located and arranged, with respect to the pilots' seats, so that there is full and unrestricted movement of each control without interference from the cockpit structure or the clothing of the minimum flight crew (established under Sec. 25.1523) when any member of this flight crew, from 5'2'' to 6'3'' in height, is seated with the seat belt and shoulder harness (if provided) fastened.
(d) Identical powerplant controls for each engine must be located to prevent confusion as to the engines they control.
(e) Wing flap controls and other auxiliary lift device controls must be located on top of the pedestal, aft of the throttles, centrally or to the right of the pedestal centerline, and not less than 10 inches aft of the landing gear control.
(f) The landing gear control must be located forward of the throttles and must be operable by each pilot when seated with seat belt and shoulder harness (if provided) fastened.
(g) Control knobs must be shaped in accordance with Sec. 25.781. In addition, the knobs must be of the same color, and this color must contrast with the color of control knobs for other purposes and the surrounding cockpit.
(h) If a flight engineer is required as part of the minimum flight crew (established under Sec. 25.1523), the airplane must have a flight engineer station located and arranged so that the flight crewmembers can perform their functions efficiently and without interfering with each other.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-46, 43 FR
50596, Oct. 30, 1978]"
In a broad sense, if a manufacturer was particularly constrained for cockpit space, then you may well find yourself with insufficient room to fit, even with all adjustable seats, pedals etc at maximum extension. What few people mention (tsk, tsk Checkers!) is that a key dimension in the cockpit is the design eye postion ("DEP") which affects how much of the instruments you can see and how much of the real world that you can see.
For example, if you have very long lower body lengths, then the control column may obscure the lower part of the instrumentation, whereas very long upper body lengths may obscure the upper part of the instrumentation as well severely limit your upwards field of view. Most tall people just end up with sore shins and posture-induced lower back pain, depending on the aircraft. Of course, I shouldn't understate the focussing problems that are brought on by having your face closer to the overhead panels.
Notwithstanding, the far greater problem arises from those folks who are "vertically challenged".