If you want them to completely clear and rotivate the whole area - you're gonna need more pigs
I've got 4 fully grown Large Blacks (plus a Berkshire) in an area of almost 2 acres, they've been there over a year and the ground is still 'unrotivated' in lots of places.
I'd keep them confined to a small area and relocate it once they've cleared it - a wee electric fence set-up as PP says would probably be ideal for the job

i am assuming they will be going for the chop when ready 
errr
no Robert
I am far too much of a softie! I have got them for their land clearing abilities-if you saw the amount of Cape Broom, you would understand
.
Are you going to breed with them ?
If you don't send to slaughter or breed you're going to end up with 2
large girls who feel like they have something missing in their lives

They may start to give you problems with escape attempts (going looking for a boar) or behavioural issues (piggy PMT is no fun !) when coming into season.
I'm not having a go at you, or trying to put you off - if you're going to breed you're going to have lots of learning to do and face the fact that some of their offspring are going to go in the freezer

Whatever you do decide though, we'll all be here to help if you need it

Karen
