[EricH]

The feed slot is perfectly fine as a source of tubes.

However, here are a few factors to consider:
*There will be defense, if you're carrying a tube. Defense subjects robots to hard loads and forces. These forces may cause tubes to leave grippers before they are intended to. Design accordingly.
*Driving all the way over to the far end, picking up a tube, and returning takes time. Wouldn't it be great if your feeders could just throw a tube out to the end of your lane and have you pick it up right there?
*You are going to place, you open your claw, and you suddenly use one of a number of 4-letter words. Your tube is on the ground, and you can't pick it up. Now you have to go all the way across the field to get a new one. Ouch.
*Your opponent (or your partner, or you) drops a tube. You would love to get that, but you can't floor load. The best you can do is shove it into one of your protected areas and hope a partner picks it up.
*In qualifying rounds, it's quite possible that you get 3 robots on your alliance that can't floor load. Every dropped tube is fair game for your opponents, particularly if they have a floor loader.

I call those 5 good reasons to at least consider floor loading.

If you don't floor load, then I would suggest making your grip so solid that the tube can't come out, unless you want it to or have placed it solidly on a peg. Plan on a 165-lb robot hitting yours at any random angle at about 15 ft/second (their speed), bumper to bumper, when you're least expecting it. Then pray that Murphy is taking the day off or bugging some other team...