Burn the ISO to another USB stick or a DVD. Boot off that, then select your USB stick as the install destination. This won't easily move to a different computer, but boots quickly and has the normal security turned on.
The other option is to use Universal USB Installer to write the ISO to the USB, but set it up with a large persistence file. This essentially works like the LiveUSB, but remembers stuff. Zero security, but remembers documents and installed programs.