Would I be able to wake up at 6 hours from my alarm clock and then immediately try the backyard and tactile visualtion technique?

I'm worried the next time I wake up between REM periods will be too short and I won't gain consciousness enough to actually remember.

Or can I set my alarm to go off at 6 hours and 30 minutes? Will that still have the same effect? Or do I have to wake up the second time naturally?

My alarm is semi-quiet and only wakes me up a little.

Thanks again.