I tested the altitude hold today. Previously I have had pretty good results with the position hold.
With the vertical gain set at 80% with the Logo 700 (default I think), the helicopter shot up and down about 1m or more, quite aggressively, before I switched off the function.
For about 10 seconds or more it just climbed and fell this distance without settling! Is my gain too high or too low, please?
I understand that the aggressive motion could be interpreted, according to the explanations, as having too high a gain, but the precision at about 4m altitude was poor. The day was quite windy with direction quite variable and gusty.
Thanking you for your help here.
Andy

It seems from what some other altitude hold questions have suggested and in ensuing discussions, that I should probably reduce the vertical gain if I am seeing such 'Visible' altitude changes (about 1-2m).
I note that the Geolink tuning advice suggests double checking servo-arm centre positions and ensuring swashplate levelling. I did both of these things, especially with the RD Lohr swash levelling tools and feel it is quite spot-on. The only discrepancy from the advice involves 0 degree pitch on both blades. I have blades which require very slight individual pitch tuning to maintain accurate tracking! (Maybe I need to buy some more expensive blades, but I have always found that even with good/best blades, that dynamic blade tracking adjustment is required!
I tend to fly with relatively low head-speeds, although I need to physically check the exact rpm and change settings with the Hobbywing telemetry which requires some further tweeking. Maybe I need to up my head-speed a little more?

Reading further questions, I will reduce vertical gain by 10% at a time and then fine tune.