I doubt I'm the first guy to come up with this but this is a little trick that I learned on my own quite a while ago. This is a pretty simple way to suspend your neck out in space without having to pop cash for a swivel vise.
The cool thing about this is that once you have your scrap blocks clamped in place, you only have to remove the clamp holding the neck and the top clamp in order to remove the neck or place it differently. When you put that top clamp in place, it locks everything into place real tight. You could go to work on the wood with a handsaw and it wouldn't move.
I have a small 4" vice that I unbolt tun thro' 90 degrees and bolt down again for working on my necks.
KInda useful, just a pain to keep unbolting, but the vice has to be removed for a work area on my bench. (Very small workshop).
Might just try your idea when I get more clamps.