For people who might wanna practice this: After whiplash jumping its important to slow down your horrizontal movement for a bit. If sharp alt hits maurice once, bounces and hits him again, reflects of the coin into maurice but 2nd bounce misses, try holding s while flying above maurice to slow down and decrease coin deviation.
There are three ways to instakill Maurice with little setup. 1, Chargeback. 2, Sharpshooter techniques like this (may require the SLAB Sharpy). 3, Sharpshooting the first projectile right as it leaves his mouth (can be done with both variants).
You gotta do it off the ground. It won't work in the air. Wait until you start getting pulled, and then jump. Try doing it earlier or later to see how it affects your height. You can practice it in sanbox.