Resizing A Spanned Volume

My server is WHS 2011 under Vmware.

I have the following virtual disks, which appear to WHS as physical disks:

4TB-A

1TB

2TB-A

2TB-B

4TB-B

And a spanned volume, which spans as follows:

4TB-A - using 1TB

1TB - fully used

2TB-B second TB is used (first TB is part of backup volume)

4TB-B - fully used

Obviously there is 3TB space free on 4TB-A. I would like to use it.

I can't extend the spanned volume into the free space, and if if I try to create a new partition there, Windows says there is not enough free space, presumably because of the spanned volume.

Any ideas how to proceed?

(Note originally the 1TB on 4TB-A was on a 1TB physical disk, I moved that to the 4TB and extended the virtual disk size under VMWare from 1TB to 4TB.)