How do I make a part really suck thermally?

[Sharpy]

So, behold! My newest creation. A big cardboard box that holds KIS items and fits the MK3 cargo bay.

 

What I want is to make the cargo bay NOT optional. With the price and mass, this part would be waaay OP otherwise.

Not through physical integration though, but making the part really be not more durable than a cardboard box. The 3m/s impact durability will probably be nerfed further. Temperature is set to paper ignition level.

But it actually took more than a couple licks of flame from a Vector before exploding. There's a bunch of .cfg thermal parameters which I don't really understand. How can I tweak it so that it really overheats very fast, has near to no thermal capacity, and dissipates heat really poorly, while absorbing it readily?