
My pup is getting close to 9 stone, so I know how you feel. iIve found the big rope toys with a knot in each end are quite good as long as the dog doesn't shake them (that hurts if you get a knot full pelt in your knee cap) but must be used under supervision, well, my pup needs supervising because he'll chew threw the knots and pull out loads of strands of cotton which I then have to pick out of his floppy lips before he eats it :(
I always have a supply of old stuffed toys and footballs that my sons have discarded. Any bought toy (such as squeeky stuffed toy) is never left with the pup or he'll ruin it, he gets to play a little game with me then it goes away for another time.
My pups favorite toy is a cardboard box (eg. cereal box), I'll put a few biscuits in it (part of his normal food ration), screw the box up as tight as I can and he loves to 'find' the biscuits inside. It does make a mess but the pieces of carboard are shredded so they can go straight into the compost :)
I don't think you're gonna find any toy that is indestructable for a giant dog (or any heavy chewer) :(