Soundposts and the like

[Gareth Hughes]

Here's a new newbie question some of you might be able to help with:

I have an Eminence Portable Upright Bass, which, in case you're wondering is an acoustic stick-bass so to speak. The portable part is the smaller body but also entails a removable neck.

So that this can be done often without the need of a new set-up each time the soundpost is held in place by a disc of wood at it's base, on the back of the instrument. I don't have a picture handy, but basically it would look like a candle on a flat plate.

My question is: why is something similar not done with regular upright basses? Is it because the 'disc' part would dampen some of the vibrations the soundpost is trying to spread out?

Thanks, Gareth