Bear with me here as my understanding of the PWM requirements of devices is not very good. I think you have read the same forum topic on google as I have?
So this is really just me thinking out loud trying to understand this better. The frequency is how often the pulse occurs, and the duty cycle determins how long each pulse is, the end result is an average voltage. Would using 125hz instead of 140hz be that much of a problem for the servo actuator? is it not the same thing?
for example using 12v for ease of explanation, 125hz at 50% DC is 6v, and 140hz at 50% DC is still 6v, there will just be 15 less cycles for every one second
I will assume the actuator is looking for an analog curve that the PWM voltage mimics. will the actuator really know the difference of losing 15 cycles? it just means that the 125 pulses are a little bit longer (4us at 50% DC)
I'd be tempted to try it first before getting complicated with converters.
If you want to request a higher Frequency, you'll be better posting on the Wiki expalining the requirements.
Don't mind me, I'm just trying to understand it better, but I'd certainly be experimenting with it. I'm more of a practical person, rather than an academic, and find it easier to understand stuff by testing and playing around with stuff