i950 support borderless printing. Next time just buy 4 x 6 paper. For the time being, just remove the excess paper before putting them into the printer.
Set the papersize to 4 x 6 borderless in the page setup.
Crop the photo in iphoto using the 4 x 6 constrain.
In print advance option set the borderless extension to the max. That should print out a beauiful 4 x 6 photo which should be way better then film process.
After the printing, you can reverse the photo to it origanal in iphoto.
Buy the way, borderless printing require OSX.2.