Read thru thread, I have Stehl Tow Dolly we bought in August. Have used it on a 2500 mile trip from TX to Badlands. SD. I have built in Surge brake on mine so I can meet supplemental braking some USA states require.
The only thing I would add is, Stehl Manual States to lock Steering. Manual will state Operator procedures.
I used 2 techniques tightening down the tires and "dimple" the tires one way on trip north, which was to drive up until tires were dimpled against stop plate, then tighten the crap out of them with ratchet and straps. This method the straps came slightly loose when traveling north over the Oklahoma stretch of rough road on way to Lamar Colorado. Note, not dangerously loose though.
The 2nd (Better Method I read about from RV old timer which we used on entire return trip)pull up car within 1/2 inch of wheel Stop on drive up ramp. Put vehicle in Park to immobilize roll. Attach straps just taking out slack. Now get back in car and place in neutral, no brake. Now tighten ratchet straps. This method will allow slight movement forward, rolling forward to stop and dimple with power of ratchet. Gets a tighter grip, and in my unscientific test traveling over same stretch of road on our return trip straps never loosened and stayed tight! You need to be within 1/2 inch or you won't get roll/dimple tire response you are looking for.
Driving over that Oklahoma Stretch of road is ROUGH and Bumpy.
I also purchased tire staps on Amazon which has 2 hooks and Cradles the tire on both side as opposed to using the single hook that came with Dolly. The dual hooks, to me give me more peace of mind that car front tires are more secure.
I have Mazda, and on lower A arm, I fabricated a 3/16 inch cable With clamps looped on each end. Where I can feed thru A arm. Then loop each safety chain back to itself. Creating small cables to loop thru in concert with chain makes it fast to connect. Note..leave a little sag to allow for wheel turns, but keep loose enough that tires will stay in wheel troughs in case of strap failure. Cost under 10 bucks.
Over all. Dollies are not too bad. I would have opted for 4 down tow. But our one car family was not willing to take a beating on trade value.