Up or Down, Side or center, it's all the same if you properly strap your bike. Now preferred is to allow the suspension to absorb bumps if trailering a long ways, and if I was going around town, I would put it on the center stand or no stand. Always chock the front wheel or snub it up to the front of the trailer, Use 2 straps in front, and at least 1 or 2 in the back for tension. A 4x4 works well to roll up against... and my favorite is the HF wheel chock, I have 3 installed in my race bike hauler, they are cheap and work well.
I recently hauled 13 bikes in an enclosed trailer (multiple trips @711 miles ea.) All with the side stand down, and strapped eight ways each.
Cheers,
Man Lloyd that's a lot of straps, I am sure they were stabilized very well! Shows the love and care you have for each of those two-wheeled beauties I am sure! And a picture of all those straps would have made Spiderman proud
Charlie