[TowerTalk] Stacking Distance 10-20 Meters?

[Rich Hallman - N7TR]

I'm getting ready to stack a "Christmas Tree" arrangement of Mono
Banders on a single mast.

Looking for an appropriate distance for separation of the following
antennas.

All M2'd antennas...

20M5
15M6
10M7

Thoughts on Distance as well as can I get away with a 1026 DOM 2 In .25
wall Mast?  Or do I need to go to Chome-Moly?

Thanks..
Rich N7TR