BT, your cart looks like it can also stand up straight; looks like the weight of the bottles would allow that. I don't think the angle would be a BIG deal, but personally unless there was a really good reason NOT to, I would opt for tipping it up straight (assuming I'm right about that option) - After nearly getting killed by someone NOT being aware OR careful with acetylene before I was 20, I tend NOT to "poke the bear" unless I already have a rocket launcher pointed at him.
I don't have any pics, but a couple of the many O/A carts (most were size 5 acetylene/330 cf Oxy) at the last place I worked (retired in 2012) were set up with full-size car tires, and heavy frames that were actually a sort of GIMBAL mount - when you tipped the cart back on its wheels, both tanks stayed vertical. Tipping it back only moved the center of gravity back a bit so you had a little weight on the handles. Most of the weldors liked 'em because you could roll up to a job, do it and move on before the other O/A sets could even be used.
Too many industrial and govt secrets in that place, so I couldn't get pics, and I never got around to making a drawing - sorry... Steve