here is the relevant extract from the BAS MH-47 readme:
"The whole of the ability to move cargo is wrapped up in the BAS_Cargo.PBO. It is quite feasible for others to add to the list of vehicles that can be slung underneath, or indeed placed inside the chopper, and that may be something you would like to do.
We have done it this way for our convenience in the future, and to allow the talented to add what they desire.
However, there are a few factors involved in the internal cargo models that are not immediately apparent.
Please note that we will not be able to provide support or help or advice or answer any questions relating to the adding of extra vehicles to the list from individuals. It requires advanced modelling and scripting techniques. Of course, in order to progress the OFP community, queries from serious and recognised Addon Teams and recognised individuals are welcomed."
so i guess you could unpbo the file and have a look at it. which i myself would never to. too scared to mess with a materpiece!!
otherwise i'm sure you could e-mail them as your point does not fall into their exemption clause at the end. otherwise the readme doesn't give any scripting code relating to jeep storage, just the in mission method (drive in back and it appears on your option menu)