Okay, I thought the short answer would be enough, but I guess I'll give the long one:
-A G36 carry handle does not mount to a rail. Just go to a G36, pull out the 3 screws that hold it on, slide it off, and look at it. It's not dovetail, it's not picatinny. It's actually double-notched, and nothing close to any standard rail.
-To cut the notches to the right width and depth would be a lot of work. The end result would be a weak plastic/polyfiber frame that was just made even weaker by cutting into it, with a nearly WORTHLESS optic. Seriously, have you ever used one? They're terrible. They often can't be zero'd correctly, and they're amazingly hard to look through.
-Do you want to mount the entire handle? Do you realize the length is from about the back sight to the front sight? I don't see anyway to make that work on an M4. And if it did somehow work, it would just look dumb as hell.
If your red dot sits too high, and you want to keep your carry handle, seriously: get a cheek rest.
-BATMAN