Thought some of you might want to know that you can get the extracted 7z version of Inkscape down by about 20-30MB with UPS (I used UPXShell, and chose the 7z version to avoid initial installation). It's still over 100MB if you leave all files intact, but I'm sure there are loads of readme-type files that could be sacrificed.
Still, so far, I have compressed all the DLLs found anywhere within the inkscape folder tree, plus inkscape.exe and inkview.exe - not yet bothered with python.exe or other files - and the app works fine.
So for those of you wanting portable Inkscape, and who have never added an app to the launcher, just put the extracted inkscape folder in the same place as your other app folders and hit Options>Refresh App Icons. Instant Inkscape!
(Not sure if Inkscape uses the registry, but I believe it is "truly" portable in this way...)