Probable reason it was stopping was that when Mike's seat contacted the throne there was no room left for the fabric. Creates an "unstoppable force vs. immobile object" problem for Poser, and the cloth sim jams. Haven't used the above method for sitting but I've heard it described before. A variation on that suggested by PhilC was to use a random primitive to push the robe towards a seated position, then export that half-sitting robe as a morph. When you run the final seated sim, run the morph on the cloth before you start the cloth simulation run. (For a totally bizarre idea, you could flip Mike upside down and run a cloth sim to conform to his backside. Flip him back around and run a second sim to let the cloth fall down naturally around body and throne.)