Hi, maybe it is just me and my anxiety when flying our bird so high but it sure seems like it takes a long time for the thing to start coming down after I pull down the gas when using AH. I was on a shoot the other day and I swear it took about 60 seconds before I heard the Vario sound. By then I had lowered the gas so much it started approaching terminal velocity. C8, MK2.1, QC-3328, FF 3-Axis w/ radians, Sony 760v. I should probably just turn off AH and descend manually but I keep forgetting to try it.
One thing to keep in mind (if I am remembering the vario tone settings right) is that the vario tones kick in based on a percentage of altitude change. If, for example, it is set to start at 10% and you are flying at 300 feet it is going to take a very fast rate of descent to have the audible tone kick in. Flying at 100 feet it the tone is going to kick in at a much slower rate. I think the rate is adjustable in MK tool. Be careful if you are flying at high altitudes and are moving the throttle low enough to hear the tones...... One thing to keep in mind, if you are flying an MX 20 for control (or many other radios) there is a screen that shows your altitude and it has little indicators next to the altitude to show if you are currently descending, staying level or ascending. If you have the ability to connect an OSD, you might wonder how you ever flew without one. Being able to watch your rate of ascent or descent is fantastic. I have found when I am ready to come down, I move the throttle stick into a position that gets me the rate of descent I want and then can just watch the altitude and descent rate the whole way down. If I am flying an X8 I know that I can come down faster than if I am flying my flat CS8 and just move the stick to the rate I want.
Also depending on how far you are out and how high, judging descent rates is very difficult. Easy to think it isn't coming down only to realize to late that you've taken off to much power.
If you have vario, you also have voice prompts, and you should enable the “Altitude” prompt. Then you’ll hear the lovely Fraulein announcing your altitude as often as you’d like her to. And, as Michael mentioned, a quick glance down at your transmitter (assuming a Graupner) will corroborate same.