I modeled my low band installation after ON4UN, using a big tower to hold a 160M vertical with about 150 radials (John has > 250) and placed the elevated 4-SQ over top.
This did not seem to work as well as I desired and I saw where W8JI contended that four elevated radials were closer to 4 buried radials.
We presently have dropped the bottom of the 4-SQ to ground level, using radials laying on the ground with approximately a mile of wire under each vertical. This has improved things, but the metal guy wires still presented problems so I went to philystran guys to prevent any coupling to the guys.
The elements are individually tuned for about 3400khz.
IMHO, Anyone planning a 4SQ should have an RF analyzer and (probably) a RF current meter for assessing performance and coupling.