Looking back through the thread, and Aussie's comments about the layer call, I had a further play and it seems that this might be the main culprit(?) as the issues were fixed when I deleted all the lines in the .sca file related to the layer call for the bitmap. Changing the V1= and V2= values seems to make no noticeable difference. Changing the 255 to 254 for the TexPoly, as recommended in the MR Tutorial, seems also to make no difference.