cargo cover for my 71 k5?

[ORNG71K5]

i just bought the orange blazer below a few weeks ago and it will be my daily driver the day i turn 16 in a few months. with that i have been very concerned with being able to keep things in it with out being stolen so i came up the with the idea to make some type of cargo cover for behind the back seat.

the picture of the k5 was taken by the owner before i bought it. currently the interior is stripped and the grey bedliner is out and about ready for a line-x spray. after that i plan on building side panels for the back probably made out of fiberglass. unlike the cargo cover picture below, it would be made out of metal or wood coated with fiberglass and would probably be wrapped in vinyl so it would look somewhat decent. how it would work. there would be some type of track that would be on both panels that was just a few inches down from the top of the panel that ran horizontally from the tailgate all the way to the back seat. so the cover would slide on the tacks all the way till it reached the back seat and still nearly touching the tailgate when closed. that way if the top were off and i was able to lock the tailgate there would be no way to steal anything under that cargo cover or even see what was under it because it would it would cover the entire area from the back seat to the tailgate. then i came up with the idea to have the cover in 2 pieces and attached with hinges so if you were to slide the cover out about half way you could fold that piece up then lay it on top of the other piece and then slide that back all the way to the seat. that way you could keep the cargo cover in the back while being able to access the back area at the same time.

i hope its not too confusing, but tell me what you think, any opinion or suggestion would be helpful. my dad disapproves because he things i should weld a metal lock box to put in the back if i needed to insure anything from being stolen, but if i were to perfect the cargo cover idea it would be more convenient and less space consuming instead of having a big bulky metal box sitting in the back.