I had it in .deb-s, but this caused problems. modest and libtinymail-* packages are part of PR1.2, when I updated them with dpkg, I could not install anything that depended on PR1.2 anymore. I'm not very familiar with debian packaging, maybe it's somehow possible to update PR packages without serious sideeffects. I settled on tar.gz, to avoid any conflicts with apt-get and app manager.