Rabbit and guinnie pigs ?

I have a rabbit now and i think he is lonely, so i thought about getting another one but i have heard that bucks together fight and i don't want baby bunnies so i couldn't get a doe. but then i thought about getting a guinnie pig.I have had a rabbit a guinnie pig together befor and they where fine, but i just wondered weather rabbits and guinnie pigs can be together as of the Weight difference and if my rabbit will beat it up. suggestions greatly appreciated.