I have created three sample pages showing dynamic progressiva loading of a panorama contained in a .ptv file. Each page shows the same image at different sizes. The image has been kindly offered by Toni Garbasso.
Each image has been divided in three rows of ten tiles each, for a total of 30 tiles.
3000x1500 pixels, 883Kb
4000x2000 pixels, 1.32 Mb
5000x2500 pixels, 1.94 Mb