I fold my Strida 5 completely, stand it against a post, then D lock around the post & around all 3 tubes just South of the seat. Have done this all over Europe (using the best D lock admittedly)
( you can use the handlebar end handbrakes to stop it rolling down)
Safe & theft-proof Strida-ing!
P.S. I saw a Brompton in Kensington High Street, locked to tree using a Snake lock.....................AROUND THE SEATPOST!!!!!!!!!! What a muppet! LOL!