Pig Tractor- Question About Timing

I'm wondering if its too early to put my pigs out in a 'tractor'...

I've only ever found info on using them to clear orchards at the end of the season so I'm in the dark on this one.

We have two pet pot-bellied pigs (say that 10 times fast)
We'd like to fence off an area for them to clear for eventual gardens but I'm wondering if its too early, as we are still in the beginning of spring here. The snow has all melted and the land is fairly dried up though. We seem to be about 3 weeks ahead in the weather department, and are only experiencing light frosts at night.

I'm also wondering if there is a standard area per pig, so I know how much to fence off.

Can anyone shed some light on this?

Can't speak to plot size but if the ground is soft and they don't need to wear their sweaters  to  survive it's not too early.  They are bulldozers after all.

Max K