Hi David,
I operate a PEG channel in Washington and have the same problem. My workaround was to run the rca output of the playback unit into an Alesus 3632 Compressor/Limiter which raised the level and stops it from clipping. There’s an XLR output from the Alesus, and I screw down the positive and negative wires to the fiber transmitter input and the channel is louder. However not as loud as the surrounding channels. Our cable company uses only the left channel for it’s PEG, if we were stereo I think we’d be on par with the other channels.