My P4 Pro V 2.0 with Windsurfers can already outfly its battery. Other than foliage penetration why does anyone need more ERP? You also run into legal issues with the FCC which limit power levels. I never fly without my Windsurfers since I can just pull them off and see the signal level drop. That proves that they work. However they must be mounted properly (reflective side out) and must be pointed towards your drone to work.
Good luck
Jim
WA5TEF
Good luck
Jim
WA5TEF