No way to force US Sub-band #2 (channels 8-15) to join Helium network reliably

[Joshbloam]

I have spent hours trying to find a way to force the modem to only send joins on US915 Sub-band 2 (channels 8-15) used by Helium. I can force the modem to use sub-band 1 by setting modem.begin(US915_HYBRID) and talk to The Things Stack successfully. The problem is Helium in the US uses sub-band 2 and I need a way to force joins on only US915 channels 8-15.

Does anyone know how to do this? My fear is there is no way to do this currently. Could someone look at creating a variation of US915_HYBRID which only uses US915 band 2 (Helium) instead of sub-band 1 (TTS)?

Currently, I can get successful joins 1 out of 50 attempts. I can provide my entire sketch if needed.

if (!modem.begin(US915)) {
  Serial.println("Failed to start module");
  while (1) {}
};
modem.disableChannel(0);
modem.enableChannel(1);  // only one enabled for Helium
modem.disableChannel(2);
modem.disableChannel(3);
modem.disableChannel(4);
modem.disableChannel(5);
modem.disableChannel(6);

modem.setADR(true);
modem.dataRate(0);  //set data rate to be 0/5, Spreading Factor 7 and channel bandwidth to 125kHz. SF7BW125

modem.configureClass(CLASS_C);
int connected = modem.joinOTAA(appEui, appKey);
while (!connected) {
  Serial.println("Something went wrong; are you indoor? retring after 30sec");
  delay(1000);
  int connected = modem.joinOTAA(appEui, appKey);
}

[Joshbloam]

Never mind. I figured out how to set a custom channel mask for US915 Helium!