Glad I've got a bit of a debate going!
Big Pistons, yep that's exactly the problem I've found a couple of times on bumpier strips (and what prompted me to ask the question in the first place). You get bumped up into the air at around 40 knots which is below a safe flying speed. So far I've managed to resist the temptation to pull the stick back - I instinctively push the nose forward on the stall warner largely thanks to my instructors drilling it into me during my ppl. The difficulty with it is the risk of overcorrection and bumping the nose wheel back onto the ground.
I guess the "maintain attitude and accelerate in ground effect" technique is actually what I've been doing albeit without realising it. I'm going to do a few experiments with this on my long tarmac base runway to build my confidence for the strips.
I did my PPL on a PA28 from a paved runway and, rightly or wrongly, I was taught to scan the ASI periodically throughout the ground roll and 'rotate'. The PA28 needed positive back pressure to 'unstick' from the runway, whereas the C172 just wants to fly off itself - so this may be the difference, and why the technique is less appropriate for the 172.