Yea it is going to be tricky but I have a good plan. Part of the reason I wanted a separate cab was to avoid that problem and also to have more space so I could run a hps. Obviously a HPS would be a joke in a space like that hence I am embracing all CFL grow and seeing it as a challenge.
The top half will be sealed with more panda film. Basicly when I have fitted the shelf permanently I will start by sealing the floor, by cover it with panda film and overlapping the edges and duct taping them down. Then I will do the same from the bottom up, so basicly sealing the the roof of the bottom part with more panda film creating a double barrier, one from the top and one from the bottom. This will be the most important part of the light sealing I need to do. Then second most important part will be the opening. Again pand film will be employed, staple gun and loads of white duct tape. My other worry was how to check if it is light sealed as I am unable to climb into that space. My plan is to put my camera on filming and then place it inside and closer her up with the bottom part's lights being on. Then take the camera out and check if I can see anything. move the camera to a different position and do the same again. If the picture is all black I win and if not I will hopefully be able to find the leaks and fix it. Hold thumbs because you are right it is going to be tricky but unfortunately I have to have this grow in one space right now.
Tested the Flower section for light leakage and there is zero. This photo is one of many 10 second exposure pictures taken on a timer to ensure she is light tight. As you can see the picture is pitch black even though the veg section lights were on at the time. 
All good man, thanks for popping in. For what it's worth try to make sure that you are using the right bulbs for veg and flower. They really are not expensive so it is worth getting good ones. Read the sticky posts on this part of the forum it is worth it trust me.
Very interesting. Strange that I have never noticed this before, it must be more obvious on some strains. Thanks for the input.
Is there a/c in the room? I sometimes run a line into my box.. Maybe there is a cheap portable one? When it gets that hot growth will slow, your buds may foxtail. 95 is a bit high, try to get it down to at least under 90. Whats the temp outside the box? I often incorporate negative pressure to force the heat to the top and have 4 fans blwing that heat out the top. That will only work if the outside of the box is at least 10 degrees cooler
at least u got another one to root on! And hopefully your clones take off.