It am what it am... I have a reference somewhere with dimensions... I think I left it a little tall. They're not glued on, so I can go back and fix them if I missed by a smidge. I just cut it off at the top of the slope sheet.
edit - I found it... the prototype added 3'0-1/8" over the original hopper... some shots show the brake wheel in the original location, and some show it moved up onto the extension. I chose the former on mine... it's easier to trim it off the extension than to modify the lower one...
Lee