[amsat-bb] Stacking satellite antennas on top of an HF beam how much separation?

I'm trying to get a Cushcraft MA5B HF mini beam back up in the air. What I'd like to do is use my azimuth rotator to rotate it and mount my elevation rotator and Homebrew 2M and 70CM "cheap yagis" up above it on the same mast. Aside form the obvious distance it will take to keep the VHF/UHF array from hitting the HF array during elevation changes, what is a rule of thumb for separation distance to keep the two systems from interacting with each other? Like so many things, this is something I used to know but seem to have forgotten in my old age. Tnx and73, Michael, W4HIJ