As someone that once worked at Skyvision dispensing advice on this system, I can tell you from experience that anything smaller than a six foot C-band dish would be a mistake. While it may sound like a great idea to take a 3 or a 4-foot offset dish and fool around with an LNBF with an adjustable scalar---and you may get reception on some channels.....there are nearly 80 video services spread out over a bunch of different transponders. Until you go to a size resembling six feet, there will be the danger of not every frequency being received. Strong signals from nearby 103 and 107 West can swamp intended digital signals on 105, and if you do not have a large enough dish to separate satellites (ever heard the term 2 degree spacing, and wondered what it meant?), the results can be disappointing.
My experience on any given C-band satellite using a 3-foot offset/C-band LNBF and conical scalar adapter is that it is highly frequency selective, with or without interference from either adjacent satellite. Not a cost effective system if you are paying for programming and unable to tune all channels because of an undersized dish.