watch The Wire or any of those DEA cop shows....the border patrol show has alot of info on traps too....those mexican smugglers find every possible hollow peice in a car/truck and fill them up.
yea you are gonna be hard pressed to find a trap that LEO doesnt know about.....smugglers at the border have tried EVERYTHING....now they melt down cocaine into solution, soak it into clothes, and smuggle it that way. (read it in maxim)....traps only work for casual traffic stops by regular cops. if a drug dog hits on your car and it gets seized, they are gonna xray the car and tear that shit up.
Dude I've seen shit hid in all kinda places it just depends on how much your hauling and how much trouble you wanna go through to get that shit out on arrival
in my opinion id weld a solid steel box lined with lead so xray cannot see it and to get it out well you will have to use a grinder or plasma cutter...im just hoping your talking about making a stash spot in your car so if your traveling inside the states you have less worry....i would still use a box lined with lead and double/tripple vaccuseal shit(put nice buds in the bag and just seal then vacu other bags so buds dont get crushed and flattened) just my idea....
If they have gotten to the point where they x-ray your car and see a lead box, there just going to disassemble the vehicle to investigate it further. They find welded box's in cars all the time