My cat had a similar problem, she was a stray and when I brought her home from the shelter (where they used feline pine) she wouldn't use the clay litter we had. I went and got some feline pine and she began using it for urinating, but not defecating.
We tried many different types of litter including Fresh Step Naturals (a saw dust like litter), Fresh Step Crystals (small blur crystal like litter), and even a rodent bedding since she seemed to prefer carpet to litter and it is soft like carpet. Never got around to trying the wheat or newspaper litters as the problem resolved, mostly. But I would never think of trying the corn litters as when corn is in a wet and warm environment it can grow a fungus that creates aflatoxin which is dangerous for cats (http://www.truthaboutpetfood.com/art...t-litters.html
I would definitely go with more litter boxes and bigger litter boxes, as this helped me. I also got to the point where I would keep her in the bathroom while I was gone, particularly if she had not gone recently and I thought she had to go. She had food, water, toys, sometimes her beloved scratching post, and of course her litter boxes. I used an old towel for a bath mat as that's easier to clean more often. When I got back and she had used the box properly, or whenever she used it properly I would and still do say 'good girl' a lot and give her a treat of some wet food. I even started singing her a song about being a good girl for making pee-pee or poopy in her litter box. I know a lot of people don't think cats really listen to what we say, but I think my relentless repetition of the fact that she needed to use her litter and that she would get a treat for doing so was part of why she finally got it.
A few times when she seemed like she needed to go but walked away, I locked myself in there with her and placed her in the box, telling her to use the litter until she did - time consuming I know, but worth it when she does use the box.
It is also really important to thoroughly clean the spots where Stan goes on the floor, you may not be able to smell it, but he sure can. Use an enzyme cleaner that actually breaks down the urine smell, use pet safe air fresheners, or even put objects in the way.
Now she uses the box with no persuasion, I still usually remind her to use the litter before I leave and before I go to sleep. I still give her a treat of some food most of the time. She has only had a couple instances of lapsing on her litter usage and that seemed to be related to a dirty box or stress.
Just keep at it, do everything and anything you can think of to encourage Stan to use the box with love, treats or food, play time, etc. Be patient, be consistent, and most of all be patient.