I don't like TM751s in the setup... if you need them, find an alternative. You shouldn't need a TM751 in the setup.
if you can, its better to modify the antenna or get a polite repeater to get the extra distance needed.
Its also better to just use separate timers on each module if thats all your doing to turn lights on and off.
macros for multiples, like motion sensor turns on light, cam and sound, plus record or to turn on front light HC C3 with macro H3.
Its also better to use ons/offs instead of delays in timers (on at dusk, off at bedtime)
I use RF to trigger my RLM20 front screw in light and my cameras at my front door setup in CM15A to transmit and a RR501 to get the extra distance at my front door.
If the powerline is not getting the signal, you have other problems then X10.
read here (all) about cleaning your powerline noise from things like TVs & PCs ect ect. which will reduce signal from X10 over powerlines.