[Dovecot] virtual namespace question

[Josephus]

Hi,

I'm wondering if it is possible to create a virtual namespace on a 
prefix other than "virtual/". My goal is to mix IMAP folders with 
virtual folders on the same folder level (prefix = "").

mail_location = maildir:/data/mail/%d/%u/

# Virtual
namespace private {
    prefix =
    separator = /
    location = virtual:/data/mail/%d/%u/virtual
}

# Default
namespace private {
    separator = /
    prefix =
    inbox = yes
}

With this configuration the folders show up on the same level, but I'm 
unable to subscribe to them. When I change the prefix back to "virtual/" 
it works, but folders are still gruoped under "virtual". Funny thing is, 
when I use a prefix something like "vfolder/", the root folder is no 
longer greyed out in my MUA (TB3), and I get a "Mailbox doesn't exist: 
vfolder" error msg if I click on it.

BR,
Jos