2 compressor pump mounting for vibration isolation

[COLOR=#383A3B][FONT=&amp]I like to mount 2 air compressors (1/2HP about 20lbs each) side by side on to an aluminum cart about 8" off the ground. What's the best way to mount this to reduce as much vibration being transferred to the cart using rubber isolation mounts? I like to mount both compressors on the same base plate and use 3-4 mounts to reduce cost but it will cause some issues when both are running causing beat frequencies. Any ideas on what the best way to go about this?[/FONT][/COLOR]
[COLOR=#383A3B][FONT=&amp]-mount each compressor on their own mounts or mount them on a common base plate[/FONT][/COLOR]
[COLOR=#383A3B][FONT=&amp]-spread the mount points as far apart as possible[/FONT][/COLOR]
[COLOR=#383A3B][FONT=&amp]-make sure base plate does not flex[/FONT][/COLOR]
[COLOR=#383A3B][FONT=&amp]-use as low as possible spring constant isolation mounts [/FONT][/COLOR]
[COLOR=#383A3B][FONT=&amp]-use a 3 point mount vs a 4 point mount

Here is pic of the compressor[ATTACH]2496[/ATTACH][/FONT][/COLOR]