Trainiac,
I have been out of town, so sorry it took so long to answer your question.
I have the Walthers 130' TT, 933-2829, but the roundhouse I have is made up of the modern roundhouse, 933-2900 and the add-on 933-2901. I installed the roundhouse 1 15/16" from the TT as per the instructions and it seems to work; however, I do not have any info about the 933-3041 roundhouse you have. I somehow got the idea that the angle of the stalls determined the distance from the turntable, but I am not an expert. You may be able to try just the floor of the roundhouse you have and see if the extended stall tracks from the roundhouse would meet at the center of the TT. It seems like it would have to and that it would just be a matter of determining the distance from the TT to the stall. Hope that helps.
Gary