The free-floating test I use with Tupperware stocks is to grab the tip of the forend AND the barrel with my right (strong) hand and squeeze. If the forend can touch the barrel, the channel needs to be opened up more. Usually a couple minutes with a round rasp will do the job sufficiently.
On the other hand, I've shot more than one Tupperware-stocked 700 that was REALLY accurate with the factory bedding, including the .17 Fireball I've been shooting for several years now, and a 7mm Remington Magnum that shot better than many custom rifles. So I tend to shoot 'em first before getting out the rasp.
