I went to Oak Hill recently
and had pretty much the identical experience:
--Did both Green and Yellow and found the latter almost as challenging as the former;
--Had one big mistake (but I outdid you, nine minutes);
--Was flabbergasted by the ferns (in one "field", they were up to my neck!).
Just got an UNO email that the Burnt Mountain courses are up, will have to try that.
I like these different ways folks are finding to keep motivated during the pandemic. Good luck with the rest of your Lockdown game.