Hi Matthew,
Although it's not a perfect solution, setting the onHoldInterval to a ridiculously small number of milliseconds may reduce the gap between repeated signals to the point that it is interpreted as a constant stream or button hold when used in conjunction with the onHold command.
Also, from what I've read on IR signals, they are usually coded as a repeating signal with a specific gap between pulses for 'hold' scenarios. I may be completely wrong on the IR signal format; my knowledge in this area (hex code strings) is somewhat limited.

Cheers // Jason