Minimal practical Trailer / Floor height - axels

What is the minimal practical trailer height I should consider, and what type axels should I consider? To make this simple, lets say to the bottom of the trailer frame. I'l like to keep the center of gravity low, and I will never be doing any offroad use.
I'll be using 15 inch wheels, and not sure if I should go with a full torsion axel or torsion half axels. And on a related note, are half axels OK to use, or do they have some disadvantage?
Thanks in advance.
I'll be using 15 inch wheels, and not sure if I should go with a full torsion axel or torsion half axels. And on a related note, are half axels OK to use, or do they have some disadvantage?
Thanks in advance.