Alpine as DomU from RAM

Hello all,
is it possible to install Alpine Linux as DomU to run from RAM? If yes, what are the steps to do so? The wiki I found explains to install as 'sys' (http://wiki.alpinelinux.org/wiki/Create_Alpine_Linux_PV_DomU), but I'd rather want to run DomU also from RAM since I have a USB stick that contains Dom0 as well as the DomU's.
How to use pygrub instead of pvgrub?
Many thanks!