Update 14th May 2020:
Today I altered the gearing on LOKI by lowering it considerably.
I swapped the 18T rear sprocket for a 28T sprocket.
Well that 10 tooth difference means you still have quite a bit of wiggle room ?
This change has made the low-end highly effective although at the expense of the top end.
My aged knees and tired old muscles are appreciating the help though.
Top end is unnecessary if the main purpose of the trike to to enjoyed loaded touring.
I think that instead of predominantly using the bottom 2 chain-rings (as I have been before this change); this gearing will mean I will be using the top 2 instead and the bottom 24T ring will be for fully-loaded pull-away's and severe inclines.
I think what you should be aiming for is middle ring and Nuvinci in top a comfortable 10mph [ with full load ] at an easy cadence.
Then ride if differently to maybe you have in the past ?
So as above the ground will be level OK stay put.
Ground rises drop straight from middle ring to lower ring then the Nuvinci can be cranked down to low as needed.
Reason well it is easier to remember , usually hills quickly over power the small engine we are and as you have some over lapping gears you will still be comfortable ?
Normally you would drop down the Nuvinci to low , then when struggling as the hill still a challenge you have to drop the front ring AND move the Nuvinci towards top ? bit of a hand full when puffing and grinding ?
Ground rises either go straight to top ring [ if unloaded ] stay where you are if loaded ! there is no need for speed when touring with camping gear IMHO !
[/QUOTE]One issue I have found it that the standard derailleur mounting has the guide-wheel perilously close to the rear sprocket even at maximum adjustment, and vigourous back-pedaling can derail the chain. A bit of modification may be required.[/QUOTE]
Which adjustment is that you are using ? is this similar to the SA 8 problem you found ?