[Russpig]

Can a male kune kune successfully mate with a larger breed sow such as Gos or saddleback? Or would he be too small?

[SallyintNorth]

No experience of this with mismatched piggies, but with mismatched sheep, all they required was some uneven ground.  So he could basically stand on a box!   

Willies generally find a way, if a way can be found  

But the anatomy is different with pigs, they have to achieve a lock.  I don't know if smaller breeds have shorter equipment, if so then that could possibly be an issue.