You shouldn't see much of a difference in POI. Just make sure you keep your form - bend at the waist and make sure you anchor properly. Your range finder should do just fine.

It's been discussed here many times. Shooting from a tree creates a little longer shot, but you are also shooting down, reducing the effects of gravity. Those two factors pretty much cancel each other out in all but the most dramatic of shooting angles. If your shortest shot is 15 yardsyou shouldn't need to make any adjustment. If you get to 5 or 10 yards, you'll start to notice a more dramatic difference in your POI.

Experiment at all yardages, it's difficult to comprehend how things are going to work until you see it for yourself.

Be safe up there and have fun!