Best dump insert for 6.5'bed

[rdharris]

I pull and enclosed trailer and do mostly lawn maintenance. I usually fill up the truck bed with grass, leaves, and brush 1-2 times a week and am looking to add a dump insert to speed up the dumping process. Truck is a 4 door silverado diesel. question is which beds work the best?? Are the aluminum inserts worth the additional cost over time with better fuel economy? most inserts I have seen dump between 45 deg up to 55 deg. Anyone have issues with the lower angles?
Thanks.