[TowerTalk] 40m Moxon over or under 4-el Steppir?

[David Aslin G3WGN]

Consulting the TT hive mind.  I'm sure someone has faced/modelled this question:

I have a 100ft tower with 16ft stub mast.  The two antennas I plan to mount are a W6NL 40m Moxon and a 4-el Ultrabeam (which is electrically identical to the 4-el Steppir).  Both antennas have similar weights and similar wind areas and will mount around 12ft apart on the mast.

My logic to date is that I'd want the Moxon to be the higher of the two, as 115ft is lower than ideal for the 40m band, but the best I can do.  And that the similar weights/areas suggest that there is no mechanical reason why one particular antenna should be on top of the stack

But, I had not previously understood the possibility that the Moxon may screen the 4-el and thereby reduce the performance of the 4-el (maybe the Moxon too?)  That might suggest the 4-el should be above the Moxon.

What does the hive mind say?  Am I overthinking this or is there indeed a preferred configuration dictated by experience and/or modelling?
73, David G3WGN  M6O  WJ6O