First of all for all those that have bad recall i would highly recommend reading this tutorial (The big thanks goes to Ataraxis for a job well done).A lot of methods are given there so pick one and use it for a few days to see if there will be an improvement in recall.
Also try to discover and prevent if there is something that knocks off your recall (some concerns or feeling bad for example.)
I know you have already read this so lets get to the alarm.

When we get to the alarm clocks,somewhere and someone mentioned that you should set your alarm 4 or 5 hours after falling asleep.Though this may worked fine with someone, i don`t really agree with it.
We know that REM occurs at sleeping period of hour and a half for the first REM periods.
(Note: I personally noticed that the last hour and a half REM occurs at 6 hours of sleep so we have 4 REM cycles with hour and a half period sleeping between them. After that, the next REM period occured at 7 hours of sleep.
I note again: This is what i personally noticed. )
If we stick to that schedule we have something like this:
1st REM - hour and a half sleeping period
2nd REM - three hours of sleeping
3rd REM - four and a half hours of sleep
4th REM - six hours of sleep
So,setting an alarm at 4 hours of sleep is not the best idea i think (and it did not worked for me).Instead of that i have used alarm at four and a half hours of sleep which gave some results but that didn`t work perfectly either.
Setting an alarm clock at five hours may sometimes work too cause you have just passed a REM period half hour ago and someone by accident can have a recall at that point but i still think that this is not the best option cause you dont actually wake up in occuring REM period.
So far, setting an alarm at 6 hours of sleep gave me the best results when it goes to alarm clocks.I dont think setting an alarm at 6 hours after you go to bed, but at the moment you fall asleep + 6 will give you the time.Some may fall asleep 30 minutes after lying in bed, some 60 minutes.This is variable for every person so make your estimated time.