Anything a fraction of the wavelength is good, and of course looping or dividing it somehow to avoid such a tall single one is a good idea. The alternative is a long wire which can be stretched out horizontally so it doesn't get in the way or need holding up. Remember many vertically mounted square or similar compound antennas will be directional, so be biassed towards the two sides for reception. Ralph's ideas are correct, as a dipole is a popular way to reduce size but keep efficiency.