I would like to use a transmitter which is modified for throttle center is default position. (springs the throttle to center)
In this case, can I start taking off using althold mode? (e.g., Solo?)
YES, I think you can.
From quick test,
I set mode switch to “althold” and make throttle in the middle.
I tried to arm, but not armed. Did you test?
Sry i may misunderstood your question.
How do you perform arm when throttle in the central position?
There is some transmitter like that.
For example, solo and DJI controller.
They are armed with throttle centered.