RF elements makes a bracket specifically for connecting the 3000s to two horns (pointing the same direction). There have been others using 3000 with horns pointing different directions.
It seems that if you want MU with 30° horns you could actually do this by pointing the horns back to back or possibly just offsetting them 30° from each other. However according to cambium doing so will have downsides for any N clients you may have.
Anyway, several threads on the forums discussing using 3000 with RF Elements horns and a fair amount of conflicting information on how well it works (mostly about MU which it appears you are not concerned about).