V3 firmware featuresThere is the V3 Coal-trol advanced menu options... You may try adjusting the HLF setting, but I don't think it is going to solve your issue, but then again I may be wrong about that!!! Give it a try, but as it reads it sounds more for how the stove ramps UP to meet its next set point as opposed to how fast/slow it ramps the feed rate DOWN...
If you are getting all the heat that you need during the day from solar, you may go into the "SETUP" menu (press and hold MENU button for 2 seconds) then 3 more quick menu button presses brings you to "MIN" , leave it on the "MIN" screen just as it is and the stove will do exactly that, ramp itself down to its minimum feed rate until you exit that screen... Basically it will just idle as long as you hold that screen... That may work for you??? Or as others have said just change your setbacks around time and temp wise to accommodate your needs...