First off, the SWR differences you're seeing aren't significant enough to worry about. You *could* optimize each one for *absolute* performance in the environment it's installed in, but I doubt you'd see a measurable difference when you're done. I've got 8 antennas on my truck, I find the interaction minimal. Surely I overload the front end on some radios while transmitting on one band or another, but receiving on other bands while transmitting isn't a requirement in my case. If you want to improve the isolation between some radios, look into getting a combination of diplexers and triplexers, available from the likes of Comet and Diamond. The port-to-port isolation on these is pretty good, and might give you antenna/radio options you haven't thought of yet.