You could take a 2215 shaft at 10.7 grains per inch, epoxy a 2016 shaft at 10.6 grains per inchinside it, cutting the 2016 short enough to allow gluing a 2215 insert in the main shaft, of course. Then use a 200 grain broadhead. If you make the arrow at least 28" long, with the fletching, nock and insert, you should be able to meet or beat 800 grains.

Don't have a clue how you could make 800 grains with a carbon arrow though.