Cannot install mac package into /usr/local (problem running with su permissions)

The qt-mac-opensource-5.2.0-rc1-clang-offline package fails if you select /usr/local/Qt5.2.0 as the install location, with this message:

Error during installation process (qt.520.clang_64.essentials):
Error while extracting 'installer://qt.520.clang_64.essentials/5.2.0clang_64_mac_qt5_essentials.7z': Could not open file: (No file name specified)

Cancelling the installer at that point causes it to just stop, so you have to do Quit and then Force Quit from the dock.

If you make the target directory manually (/usr/local/Qt5.2.0) and chown and chgrp it to your own user name and group, then it works fine.

So it seems to be a problem with whatever happens to give su access..

We would like to be able to have our users install Qt into a standard location such as /usr/local so that our pre-built app can depend on it being in that location. This was not a problem with version 4.x where it installed into the global frameworks directories, but Qt5 apparently works differently.. not clear why..