It's so enduro to run 800mm handle bars! Wider bars equal more stability right? Short answer, yes. Long answer is well, pretty long.
The bar width debate starts with increasing the stability of your riding and stops with the health of your shoulders. At 6'3" an 800mm bar allows me to get into a super comfortable position while maintaining external rotation torque on my humerus and ride a super stable platform. Perfect world right there. More often than not sacrifices are made in the shoulder health department to increase the stability/ride quality via a wider bar. Are your shoulders painful? May be time to assess your position on the bike.
First, the humerus is generally in its most stable position while in external rotation and with a properly stabilized scapula. The shoulder blade itself should be seated both slightly backward and downward. The opposite position, humerus internally rotated and the shoulder blade forward and upward is not only not optimal in regard to muscle activation but also adds injury risk to the joint. We see impingement like symptoms and anterior shoulder pain ie bicep irritation show up with this positioning.
Below we see Aaron Gwin, shredding a downhill run harder than any of us mortals can imagine. Notice the shoulders are not elevated up near his ears and he has slight external rotation at the upper arm. The man has incredible strength. A strong posterior rotator cuff and global scapular musculature makes the difference here. Often we see the elbow flare upward significantly as the shoulder shrugs. Its quite difficult to assess your own position while riding so have a friend film you while descending. Assess your shoulder position and elbow positions. Are you able to maintain external rotation torque while depressing the shoulder blade down toward your back pocket? If not, you may benefit from a narrower bar. Do some experiments as there is no one size fits all answer here. In the clinic we use wireless EMG to assess muscle activation patterns with various bar sizes but you can experiemnt in the field with a cell phone camera. Find the balance between how your ride feels and how well you can control your shoulder/elbow position. That perfect balance is probably not at the 800mm mark.