So sorry your problems are pretty persistent... wow...
i know it is no fun..... remember my previous posting?
With Venus, it happens the few days after she arrived. Her tail is so fluffy and her hair is rather long.
i gathered WHY she soiled herself before. She was in the litterbox, fiddling with her businesses with her paws. In a feeble attempt to cover her stuff, i guess she accidentally rubbed herself on it. These days, she just do her business, cover it real quickly, and get out of the litter box (otherwise, i will be there to carry her out.)
Would you consider another type of litter? Also, does your litter box has a cover? Would you consider quickly carrying Simon out of the litter box immediately after he does his business?
i would hate to see his hair butchered. When i was a kid, i butchered my Japanese Chin's (a dog) hair at her hind areas, and it was really an ugly sight. Also, she might be cold over there.
Sounds like you need to watch Simon more, and observe what he is doing wrong. i did the same with Venus.
Don't know how much i have helped. Jenk, sorry you facing with such frustrations and so much clean work. Been there, done that. It is not fun at all, i know.
Take care and happy Friday!