Yep, use the mixer delay. And you only have to delay it going from acro to the altitude mode, usually the down direction if your curve is above the xy crossing point in the curve editor. Look at the servo output screen on the RC to test it before you fly it.
Normally with the collective in the middle, the output on the channel 3 will be above 0% (range -100 to +100) to get the collective to line up. When you flip to the altitude mode watch the bar and with the delay in the correct direction it will go to 0% for the altitude mode. I use 0.7 seconds, which seems to work pretty good.
I’m not exactly sure why there is a delay going from acro to altitude hold (or any mode using it). But going the other way from altitude hold to acro the switch is instant, so no delay in that direction.
And here’s the nice thing about using the RC when you have a fuel helicopter; at gross takeoff weight with full fuel you will need one curve that is a bit more aggressive. After an hour long flight with all the fuel burned off, you set up a switch to flip in a different curve for min fuel weight that lines up with the fuel gone. Curve 1 is my minimum takeoff weight curve, Curve 2 is my maximum gross takeoff weight curve. That’s why I like the RC curves better than using the IM_STAB_COL’s. The IM_STAB_COL’s are probably ok for fixed-weight helicopters. But I don’t fly those.
I have Taranis radios and I have a different setup than ArduPilot has because my governor is on Switch E. With the switch down there is no governor, no curve. With the switch in the middle or up, governor is on + Curve 1 in middle, governor on + Curve 2 in the up position. So one of my pre-landing checks after a mission is to flip the governor switch to middle position after a long flight with the fuel burned off.