Easy to do, problem is you have to reset the chip. Chip reseters for the 9880's were very cheap, around 20.00. So far all I have found on the 9900/7900 cost around 100.00 to 125.00 and I can buy plenty of new tanks 3 at least. If you find a chip resetting device in the 40 to 50 range, I am also interested.
As for padding, anything absorbing works, plus, you can move the left one to the right just as the right side gets to around 90%. The almost full right now in the left will sit there for a least 9 months before it finally gets full. All the ink goes to the right tank. And unless you do a lot of full sized prints i.e 24" full bleed, it seems the left tank does very little. It's used during PK and MK swaps, I have tested that.
Paul