I have read in a couple of different posts about brakes not setting imediately when you use the manual slide, one person even said their brakes did not set until rolling about eight inches. I am curio...
Just raise the jacks so that they are just slightly off the ground then PULL with brakes on full manual. If the hitch is not latched, the 5er won't fall on your truck.
Don't rely on chocks to hold your rig as that will not test your brakes.