after adding qxl graphics, the memory option of qxl is locked to 16 megabytes and the headers are locked to 1. if possible, and if it makes sense (i.e. if its possible from the qemu side) it would be nice to have these settings unlocked.
QXL ram is mostly only interesting for multihead AIUI. Regarding making 'heads' editable, we should only do that when virt-manager can actually handle multihead in some usable way, which it currently can't. Duping to that bug *** This bug has been marked as a duplicate of bug 885806 ***