Check your Tail press tutorial though, think you forgot an "e" in spine. Which brings my question, so when lowering your body before popping, you do recommend to hunch over a little at the spine while not breaking at the waist to keep your shoulders above the board?
Thanks for mention about the 'typo error'.
In regards to having a slight curve in your spine. In my opinion yes. As you contract and get smaller, flex all your joints and just let the spine curve naturally.
You should ideally do this to counter the movement of your hips over the heel edge. As you compress and flex down, you will naturally shift weight over your heel edge slightly, via your hips. The curving, or 'hunching' as you mention, of the spine will counter that movement. It will make the movement of getting low feel more natural, helping you stay centred over your board.
The same also applies when landing on kickers etc, or any big drops with large amounts of compression or flat landing, cliff/street etc.
Don't try to keep a straight back. Let the curve in the spine happen. However, as you do point out above, this curve of the spine is not to be confused with breaking at the waist/mid section.
I often see people flexing down and not letting the spine curve at all. What happens?: The hips shift over to the heel edge with no counter balance going on. This can lead to the board turning in that direction, then when they come to extend upwards (say they are going for a jump) they end up taking off on the heel edge.
Too much curving of the spin (breaking at the waist) leads to the opposite. So we need to find a stance somewhere in between. And that takes time and practice. Try to feel lots when riding, it's your bodies way of giving you a private coaching session!
I know that was probably in a little bit more depth than what was required for your question, but I just thought I'd mention a wee bit more for others out there.
Glad the tips are helpful.
More to come soon.