This is how a Wingsuiter should NOT be exiting your Skydive Aircraft. This guy is very lucky that he did not strike the horizontal stabilizer, severely injuring himself or even bringing the airplane down.
As a Skydive Pilot in Command you need to be talking to your skydivers (especially Wingsuiters) on the ground regularly. Also, at the start of the day or in between loads when you have a chance to talk to a Wingsuiter that you do not recognize at the DZ, go introduce yourself. I always do. I also ask them how many wingsuit jumps they have and I remind them to stay tucked until they are well clear of the aircraft.
A few years ago I had a Wingsuiter open up (his arm and leg wings) too early and he struck my horizontal stabilizer. The strike only slightly dented the sheet metal. However, it broke his right arm severely, which made it much more difficult for him to deploy his parachute and manipulate his toggles.
Luckily he landed safely. I waited to yell at him until after he returned to the DZ with his cast on and his pain pills in full effect.