If you're getting too much zoom creep, buy one of those silicon "charity" wrist bands (I got some black London 2012 ones).

Put them on the lens so that it's all on the zoom ring, and then shift it so that a bit of it is over the barrel on one side of the zoom ring.

Play with it, you can make it stiffer by having more of the wrist band on the barrell.

I've used this to "play" primes. Working out which focal lengths get me which shots in practise, rather than looking later while in PP.