Hi,
We to have a youngster who likes to wake early. We also use the foam installation and over time have come up with this idea. I have cut the pipe to length and shape and place 4 bits on the edge of the window sill and then bring the net blind down. This holds these bits in place. We also then clip another lot on the bottom of the black out blind and this creates quite a good seal. I have used the 22mm size pipe installation on the window sill and 15mm size on the black out blind. However the little man still like to rise early, so as soon as he could read numbers I installed a digital clock and he knows not to get out of bed until at least 06.00. However it doesn't always work as it was 05.28 this morning! It also helps to either park the car close to his window or park away from the sunrise if possible to shield the window.