Just a follow-up on this issue, the problem was the environment variables coming out of the sbox setup; there'll be a fixed sbox version out soon (looks like it'll be 1.11.6-1), but the latest git versions have it working (as of commit ded0000592 in gplhost.com sbox repo).

For anyone needing a webhosting control panel, I'll say this setup looks very nice, using the dtc package with the sbox_aufs security mode. You get a nice chroot separation for all your accounts. (Note, I'm just an end user, not selling anything, it's all free software.)