Several of our projects have 100+ feet of cat 5 between the RP-6's and the RM-433 modules. The most RP-6's on 1 single job I have used is 5 with 6 RM433 modules all tied together via 1 continuous run cat 5. If you put RM433's in the attic try to put the module as close the drywall ceiling as possible, and let the antenna portion poke up throught the insulation, this reduces the amount of heat and cold it will be exsposed to.