I have been using what seems like the easy method with success.. just drill a hole in the ink chamber, fill and plug.. I see other instructions with two holes.. removing the ball ????
Whatever works! I use the technique you do. Just be sure you get an airtight seal after refilling. I use the stainless steel screw/O-ring seal technique and I've never had a cart leak into the printer. You do have to occasionally change the o-rings as the stretch and flatten out.