I have adult pigs on an acre, well there is a pen with access to the acre, so we can restrict them if necessary, but they spend all summer out there. they havent trashed the whole thing, they tend to stick to 3 or 4 favourite digging sites! I would think that 2 fatteners for 6 months would be fine, giving you a chance to repair if necessary over the autumn/spring ready for the next batch. Or you could split it in half, use half one year and the other the following year? either way I dont think 2 weaners would do that much damage to a fairly large area, the other thought also is that they will grow quicker in a smaller area, you may not get them to porker weight by 6 months if they have too large an area, of course others may disagree but thats my experience.