boot from PXE

Hi,
I'm trying to setup what's needed to boot AL from network. I did follow http://wiki.alpinelinux.org/wiki/PXE_boot and have dhcp, tftp and http running fine. On the other hand, NFS-server seems broken in AL as it did not start (see http://wiki.alpinelinux.org/wiki/User_talk:Jch#NFS_bug_study).
I'm trying the PXELINUX path.
I want to start a new KVM or physical box to boot as it was from USB with apkovl comming out the http server.
I did made a pxerd with needed network parts added with mkinitramfs but it doesn't seems right as it fails to populate the initial rootfs and to download the modloop squasfs file.
I guess either my pxerd or my pxelinux.cfg/default is wrong. But I still cannot figure it out :(

PROMPT 0
TIMEOUT 3
default alpine
LABEL alpine
LINUX alpine/vmlinuz-grsec
INITRD alpine/pxerd
APPEND ip=dhcp modules=loop,squashfs,usb-storage modloop=http://192.168.1.2/grsec.modloop.squashfs nomodeset apkovl=http://192.168.1.2/configs/"{MAC}".apkovl.tar.gz

At startup, the boot process starts AL but fails in the init script with "failed. initramfs emergency recovery shell launched. Type 'exit' to continue boot"

I suppose it is because I did not specify an alpine_dev option in the APPEND line to let AL find needed LKM. But there is neither one in the wiki example... And I dunno what to put in such place. On a USB running machine, it seems to point to the first partition (the only one in fact) of the key.
Or because modloop is not properly downloaded from the http server (nothing in the log). But modloop (as defined in the wiki) in not present as an exlicit option in the initial init script...
Or something else :(

any help or ideas are appreciated.
Kind regards,
JCh