tuning on neck-thru question

[@war]

Hi guys

I just got a neck-thru bass, and noticed that when I tune, if I tune with the bass against my body and get it perfect, then let it hang in mid-air, the strings aren't in tune anymore (they only go like 5 cents out), and when I bring it back against my body they are again. Is this due to the slight pressure my body applies to the bass or the difference in distribution of weight on my strap when hanging free vs in playing position? Is this normal?

I never noticed it with my bolt-on before, and that was a much cheaper instrument, but I can't say I ever really had the oppourtunity to notice... Was a pretty random happening.

How much should the neck move?

Sorry if this is a ridiculous question!!!

Thanks!
Andrew