There is no recommendation. How far apart the mesh APs are depends on a) requirements in your design, b) your requirements for throughput (if any). So you either have an environment where you require APs as specific locations, you are placement restricted and you use the antennas required to hit bandwidth targets, OR you have bandwidth requirements but placement isn't as critical, and so you place the APs at locations based on your performance requirements. The outdoor VRD has some guidance on Rate v Range, but right now we have validated 275 mesh, 277 mesh, and 274 with ANT-2x2-5314 antennas. If you give us the separation, we can give you an estimate of performance, but as with any prediction or in our own measured tests (which are done in RF clean environments with noise floors at or below -100), your actual performance will be based on the environment you have.