Well, I cant understand the perforated OCDC on the Dixies either. The holes let some grass pass through, then it clogged and prevented all grass from shooting out anyway. They should just make them solid and be done with the holes.
If your going to make a dedicated mulch plate, you need to do more than just block off the discharge. What type of mower do you have? Make sure whatever kind of plate you make that if runs in and follows the contour of the discharge blade arc. Truthfully, each blade should have its own shrouded mulch plate.
Good Luck though!
2004 GMC 2500HD Reg Cab BOSS 9.2V
2006 60" Hustler SuperZ 28hp EFI
1996 48" SCAG Belt WB 14hp Kawasaki
1998 21" Lawn-Boy 6.5hp Staggered wheel push
Various Echo 2 Cycle equipment