[Antennas] antenna tower separation

[Billy Cox]

A couple of ideas to ponder perhaps?

The ARRL Antenna Handbook has a software program called
HFTA, this is an excellent way to determine, based on
your actual terrain there, what are "best" heights.

As to the antennas/towers not "seeing" each other. Consider
placing them in a line of North to South. For most times
at HF, you will rarely be pointed due North or due South.

Hope the above helps to think and plan out your next steps.

Happy New Year,

73 de Billy, AA4NU