That certainly could work...But as they say, the devil is in the details. :-D
What will be the temperature during this time? If it's too hot, it could be a problem, 4 hours isn't a terrible long time, but at high temperatures, it doesn't take long to cook some bees.
Be certain they don't have another exit point.
If your assumption about them not going up as high as you will be cutting is wrong, things could get ugly in a hurry. :laugh:
I'd would definitely cover the entrance before sun up.
If you are worried about heat, how about stapling a piece of window screen over the entrance?