Converting PVE 2.3 sparse raw disk to unsparse raw

I have several raw disks created in Proxmox 2.3 that are sparse. I would like to expand them (unsparsify them).

So far I've tried:

cp -sparse=never infile outfile
scp (doesn't support sparse files, should expand them autmagically)
qemu-img convert from raw to qcow2 and vmdk and vdi
vboxmanage convert from raw to vdi and vmdk

In each case the output is still a compressed volume and I cannot mount the filesystem as the LVMs appear to extend past the end of the physical disk. Are you using a proprietary compression on your raw files?

Thanks!