Minutes ago I "emerged" for the first time successfully a package via portage (the Gentoo-package manager): vim - automatically including 5 prerequisite packages.
I had to add some users to make Gentoo happy but the whole boot process and save-file management is done by (modified) Puppy-scripts.

The Gentoo portage-tree is stored in two separate image files (ext2 & reiserfs) which are mounted onto /usr/portage and /usr/portage/distfiles.
Everything is running from an USB-flash-drive which of course should have a minimum size of 8GB ... (to store Gentoo repositories) - the base image files are much smaller. One will also need lots of RAM for compiling packages (all compiling is done within the Puppy-ramdisk).
I will keep you updated and will offer the base-image-files for downloading and testing as soon as the project reaches beta-status.