I have my frogspawn, about 8" apart and about 10" on the other side of tank and have never had any problems. Here is just something from a livestock dist...
During the evenings, its sweeper tentacles can extend up to six inches beyond its base into the reef aquarium surroundings. It will sting other neighboring corals in the reef aquarium, therefore, it is best to leave plenty of room between itself and other types of corals.
As it says "other corals" I am not sure if this means other frogspawn, some1 with exp. in this would be great 2 hear from as mixing colors may look nice.