What bitch?
The only limiting factor on these is how much pain you are willing to endure. The first time I tried these I went up to 365 and had huge bruises on my forearms for a couple of weeks. Just try to hook the bar as best you can in your elbow then I like to put my hands together both facing up and hood the thumbs together then grab around the palms to lock in my grip. Balance is also important so I usually to a "test" pick up where I don't lift the bar all the way off the rack so I can see how the bar feels on each arm. Some guys I know where a sweatshirt so the sleeves act as pads. Personally I like the pain.
Cheers,
Scotsman