I was in on that cheap drum buy, and the conversation on modifying the guard. Much wailing about posting not-deals occurred in that deal thread, so I'm closing the loop here on my version of the mod...
I completed the modification today, and it worked great. Instead of slotting the holes, I cut the "flat" face from the "curved" face at the intersection with my bandsaw, splitting this into two parts. I then cleaned up both parts so I could re-weld the joint after repositioning the curved face to clear the large drums. I placed a drum and fitted to insure there was clearance.
I learned that you could lap the two pieces the opposite way they were originally while pressing the curve piece tight against the tool case and get ample clearance. I then tacked, removed and welded the seam, did some grinding and dressing, tossed on some fresh paint, and reinstalled. I had to make a tweak in the vice to make up for a bit of weld shrink, but otherwise it works factory.
It took 20 minutes.