when to feed rabbits to a boa??

[djc3674]

Just wondering how big a boa should be before attempting to feed a small rabbit. My boa is 6ft+ and jumbo rats put nice lump in him but not a huge one. As you can see in the pic...he has a jumbo rat in him. Also, if and when I do try rabbits I am assuming I should kill it first (if he will eat it dead) or are rabbits better prey for bigger snakes like burms and retics? Here is a pic of him in his old tank, taken almost 2 months ago and he has shed once since then so he is a bit bigger. I know he is 6ft because the new tank is 6ft long and he goes all the way across it with a few inches of his tail leftover.