i did the same mod for my dX6, when i put a 6db between the DX6 and the transmitter, the small green "TX" light went off fairly quickly, with a 3 db it lasted a little longer, now I'm running it without any attenuator, works great! and the 6 db 2 watt attenuator on the output gets warm
. i was also concerned that the attenuator may also limit the dx6's ability to find a clean channel.
I'm thinking the dx7 must have more power output.