Apr 2014: I purchased a Rubbermaid Commercial FG750831 Auto Flush Tank for a great price on eBay and have had it for a few months, but finally found the perfect mounting location in April 2014. I placed those empty litter jugs around the toilet to keep them from pooping on the floor where it is hard to reach to clean. Yes, even at this point, poop on the floor will happen. The auto flusher continues to work in 2016. It exceeds expectations and without it, I do not think we would have succeeded, as they will avoid using the toilet if it is still soiled.
I eventually removed the citikitty insert and simply use the white Litter Kwitter seat permanently. I have brought the Litter Kwitter toilet seat to motels on two occasions, and the cats have been able to use it. Sometimes a few drops of urine would land on the inner rim of the seat. I remedied this by using a jig saw to trim away the rim in the two top corners where my cats usually sit.
(2016 update): My male cat is great at using the toilet. Sometime after training, my female cat eventually decided she'd rather just poop on the floor next to the toilet. When I am home, I can shout/snap and she'll hop on the toilet to poop, but otherwise she prefers to paw at the floor for several seconds then just poop on the floor. I've come to accept this as I do not want to put her (and myself) through the stress of additional training. Cleaning it up takes less than a minute to pick up, spray, wipe, and flush down the toilet. No dust, lingering smell, or hassle of a maintaining a litter box ever again.
One issue I now encounter, though, is coming home after a long day needing to use the bathroom badly. But I come home and wake up the cats from their day long slumber, and they both have to use the bathroom too! So I must wait in line.
for previous progress notes, see videos 2/4 and 3/4.
I tried CitiKitty for a week or so in September 2013, but it didn't hold enough litter and it was so difficult to clean. The kittens didn't like it and wouldn't use it. I tried various other DIY methods except nothing was really stable and secure enough.
In October 2013, I purchased a used Litter Kwittter off eBay. I ended up buying the multicat intermediate rings as well. I also used the thin flexible cutting boards and hot glue to secure a cut out oval shape the size of the whole ring, then making a hole in the middle I would enlarge slowly. I used Better Way Flushible cat litter. A large bowl within the toilet can help catch litter in the beginning when there are large amounts being used.
Notes: My kittens were about 4-5 months old by this time, and had used a litter box adjacent to the toilet for 1 month prior to this. This entire process took several months and was the single most challenging task I have ever done. More difficult and time consuming than grad school. In the beginning, you need to be there when the cats show signs of needing to go. For me this involved creating a spreadsheet tracking feeding times and logging when they urinated and defecated. For a kitten, this is several times a day, double that if you have 2 kittens. You may end up sitting in the bathroom for hours. You will get stressed and frustrated and spend many hours google searching and reading forum posts. You will have to sacrifice all your time. If you are a stay at home parent, a retiree, or a student with short class hours, it is possible. If the cat will be left at home for 8 hours when you are gone at work then forget about it.