MIMO 4x4 directional antenna set

4x4 antenna mimo
For Roof Mast mounted direction gain log periodic antennas…

MIMO 2x2 is two antennas 2 to 3 feet apart (vertically or horizontally from each other where one antenna is polarized at -45 degrees from vertical and the other is +45.

OK. Then what are mounting, separation and most important the polarization angle for 4x4 MIMO?

Would that be (Vertical, Horizontal, -45, +45)? What is a reasonable CTR2CTR distance?

Application is a FIOS failover solution using 4G LTE carrier aggregation in a low signal area. The CAT-18 is using 4x4. I need a bunch of gain, so a prefab single antenna is not going to work.

What the actual antenna spec best practice for roof mount directional gain units for 4x4 MIMO?

Thanks in advance.

so there is no specifics on how to orient 4x4 MIMO antennas for the Peplink modem?