I stop every time at both Ag stations and weigh stations with my Grand Cherokee pulling a 7x16 tall cargo trailer. It is privately registered, but has the website of my business on the back. So, I stop just in case. After all it does say "ALL TRAILERS" on the sign just before the checkpoint station.
As mentioned above, the LEO's are trained to ask questions and evaluate the responses. Only once did I have to open the trailer for inspection. The LEO at the booth said go ahead, then a second LEO about 100 feet later flagged me down and had me open the trailer. (I had the small 7x12 cargo trailer that day.) He took a quick look inside, told me to go, and quickly moved on to another trailer. It was quite obvious that they were looking for something very specific that day. We didn't have it.
Personally, I would rather err on the side of caution than to irritate the inspectors. They have a job to do to keep the public safe, whether it be overweight vehicles, fruit-flies, contraband, or anything else that could be a potential problem. The few minutes that it adds to my trip is negligible.