Wireless Joint

I purchased a pair of dual band parabolic grid antennas two years ago. I mounted them on a mast, one above the other. I was told to set them up at 45 degrees and to keep them 3 feet apart. Now I am reading where they can be installed within inches of each other.
So my question on that, can the two grid antennas be mounted within a few inches of each other rather than the 3 feet minimum? and of course installed at opposing 45 degree angles.
Somewhat related.....I had the two grids on the pole, one above the other. Would there be any benefit to mount the two grids on a piece of pipe and then bolt that to the top of my mast.....so then the two grids would be mounted side by side rather than stacked. Does one method seem to show better results than the other, or doing either way pretty much equal?

thanks!

I think that if they are polarized, tilted opposite of each other by 90 degrees, it should be relatively fine to place near each other. Technically space is best though, if you are going for optimal placement for the clarity of the RF signals.