I rely on simply watching -- and on the small 1/4" thick foam thingies - they fly pretty darn flat at say -10-15 mph
In fact -I can not detct any AOA as they fly by --and I can fly em 5 ft from me .
as soon as you get below say 10 mph -- the required AOA becomes noticable
as you slow to say 5 mph (walking speed) - you get a lot of sink OR you can power neatly into vectored thrust flight.
I have tried squezing LE to lesser thickness. but of course -there is no way to see any change in performance .
I really don't know how low the AOA really is at say-- 30 mph and I daresay any calculation at this would be very chancy as I would bet the thing is actually bobbing along and never holding a fixed AOA
Indoor gliders and powered stuff -such as microfilm ,fly in pretty still air and at walking speed which is more or less, a small speed envelope and I can see where a foil could likely be optomized for these parameters.
These little thingies I am playing with have a very broad speed envelope -I have had em reverse/ flex /whatever in a high speed dive and on anything else -an explosion of parts would ensue--
But The medium is so cheap and easy to work with - a max failure will only cost lunch money to replace.