Here is the ISF rule,
RULE 6. PITCHING REGULATIONS (Fast Pitch Only).
N.B. The EFFECT for all Sections 1 - 7 follows at end of Section 7:
Sec. 1. PRELIMINARIES.
Before commencing the delivery (pitch), the pitcher
a. May not take the pitching position on or near the pitcher's plate without having the ball in his possession.
b. Shall not be considered in the pitching position unless the catcher is in position to receive the pitch.
c. Must have both feet on the ground within the 61.0cm (24 in) length of the pitcher's plate. The hips shall be in line with first and third bases and both feet must be in contact with the pitcher's plate.
d. Must, while standing on the plate and with the ball in either the glove or the pitching hand, take the signal, or appear to be taking a signal, from the catcher with the hands separated.
e. Must, after taking the signal, bring his whole body to a full and complete stop with the ball held in the hand or glove with both held together in front of the body. This position must be held for not less than two (2) seconds and not more than five (5) seconds before releasing the ball. NOTE: Holding the ball in both hands to the side of the body is considered in front of the body.
Says nothing about any pins in the pitching plate. Only says the feet must be within the 24" width of the plate.