[arch-releng] AIF Install Troubles - Encrypted LVM

I am trying to make an AIF install script by modifying the "fancy-install-on-sda" example. My troubles lie at the very end of line 35. https://github.com/Dieterbe/aif/blob/master/examples/fancy-install-on-sda I want to set the home partition to extend to the remaining free space, but I don't know what token or variable to put there that AIF recognizes as the equivalent of '+100%FREE' (which I have tried with no success). Any suggestions?