[TowerTalk] Phasing stacked tri-banders (or, "can you check my homework?")

[Tom Sessions]

Could incremental lengths of coax be used to phase two different antennas?

Just suppose I have a brand M 4 element monobander and a brand H 6 element
monobander, each for the same band, stacked on a rotating tower.  I have no
idea of the length of the feedline to each and I want to feed them together
for biggest DX signal.

Could I add coax increnentally to one of the feedlines, and then transmit a
signal thru both simulatanesously to be received at a distant ground wave
station in order to determine how much extra coax would bring the signals
from the two antennas into phase. I am thinking that the length of extra
coax yielding the strongest received signal at the far station would
indicate proper phase for DXing.

Lengths of 1/10 wavelength,  2/10 wavelength, 4/10 wavelength and 8/10
wavelength, just four lengths of coax, would incrementally cover every
tenth of a wavelength for the experimental coax.

Anybody tried this?
Comments?
Suggestions?

thanks/73
Tom K4RV