I own, and have used quite a few Matrix's and only 2 had the wall tension set right. Just go in and on the inside there is a buckle at the top of each corner. Just un-click the buckle on the first corner put about 1 inch more of slack in it and click it back into place. Then follow that around the whole inside of the blind going buckle to buckle till your back to where you started.
It may not seem like you're loosening it much when you first start but when you get to the last buckle as a "whole" it will have loosened plenty and you will be able to set it up and take it down in a flash. I think it takes me an average of 45 sec.. but wall tension really aids in that.
Hope that helps, or if you have any other questions PM me.