only works under 2.30 and use this method:
0-I assume that you have your PS3 connection configured to use the proxy.
1-Run the PS3.Proxy.Server.GUI, tick the PS3 option and Start the proxy.
2-Enter to the USA PSN Store, and browse until you find the demo that you want to install and start the download
3-Cancel the download immediately you see the download bar
4-Open the PS3.Proxy.Server.GUI and go to the Logs tab
5-Right click to copy the URL of the game
6-Go to the Replace Files tab, press the Add button
7-Paste the link you copied in the step 5 in the left field
8-Select the small button in the right field and browse for the downloaded PKG file
9-Select to download the demo again on the PSN link
10-Wait until it installs the demo.