Despite all adjustments that we've made with the hitch (in its lowest position) and the pinbox (in its highest position), we're still towing a little nose-high. The weight distribution of our 5er is ...
The only safe way to do it is cut the spring hangers off, weld on a piece of box tubing to the frame and then weld new hangers in place. How nose high are you? An inch or two is no big deal. Clunking could be caused by loose fitting between pin and hitch jaws. Thats where mine comes from. When it gets noticable, I adjust the hitch jaws a bit tighter.