These parameters are essential for the proper function and timbral characteristics of the pipe. They are related to frequency, power, and blowing pressure. Here it is difficult to give any specific recommendations to follow, there are many alternative ways to specify. Applies to the open end of open pipes only. There are some factors you must account for when calculating the physical length.
First thing is to decide whether to make an open pipe or a closed pipe.
Generally open pipes are somewhat louder and have stronger harmonics, richer timbre, than closed pipes. The length of an open pipe is somewhere near L, at its basic resonance it contains a half wave of the sound. To fine tune it a convenient method is to cut down one wall of the pipe at its open end and to partly cover that opening with a plate that you can slide up or down. To fine tune it you plug its end with an adjustable stopper. With a closed pipe you subtract only once the width.