How small can i make sandbox partition

[Dutchray]

Hi,

i'm a new and very satisfied user. I have a question about the size of the sandbox partition. Per the instruction in the manual I have made that partition 15 GB. After making the safety clone, I see that it's only using 6 Gb of the available space.
Obviously I would like to use those spare gigs for better use. Could I repartition and make a new sandbox partition of say, 9 Gb, or would that be unwise?

Thank you for your reply.

Ray