Bed Lift Kit

I have a 2010 172 pod with the bunk beds on one end.  The whole area under the bottom bunk is a storage bin.  I would like to put a bed lift kit on this bottom bunk to help in raising the bunk, and holding it open while I put in and take out items from the bin.  The top of the bottom bunk bed is the standard thickness plywood that came with the pod, OEM from manufacturer.  On top of that is the 4 inch foam mattress and we have a mattress cover on top of the mattress.  My question is:  What size strut kit do I get.  I don't want to get one that is too strong so that the bed will not let down, and I don't want to get one that is too weak to hold the bed up.  I guess what I am looking for is advice on a pound rating for each cylinder and a place where I can get the kit.  Any advice will be helpful.