My dog breaks of my camper shell!!

So I purchased a used Leer camper shell with dreams of keeping my pups in the bed. I just had a kid and although my Cattle Dog usually rides shotgun, she has taken an interest in harassing the baby in the back. Australian Cattle Dogs are incredibly smart and loyal creatures which is what drew my to the breed. We mountain bike and fish together and she is never more that 5 feet away from me. Anyway, I put her in the bed and shut the the shell door for the first time and I shit you not before I was back in the drivers seat she had figured out how to use the interior safety lock to open the door and she's running the the passengers seat.

My question is, has anyone else had this problem with their cap and their smart dog? how have you fixed the problem? I am hesitant to file off the safety latch but I fear that may be the only option. on a side note, this system does not look very secure as anyone with a hanger could access the contents of my bed in a matter of seconds.

here is the culprit. (different vehicle)

 

Neither of my dogs like being in the back. One of them acts like he is dieing if he is more than 5ft away. You could try putting up a fence.

It would somewhat restrict access to the back but it pops off in 2 secs if you really needed it off. I say somewhat because you can reach under it depending on how high/low you make it.

 

Harness with leash attached to carabiner bolted to floor of bed out of reach of doors somehow?....

 

wow I knew someone would have a good answer to this issue! I like both ideas and they certainly both solve the problem I will probably wind up using the leash suggestion until I find a gate that will work. thanks guys!