Recommendation: If you do have a soft sided rolling briefcase that fits in UAXs RJ145s and 200s and it doesn't have a strap or the option to use a strap, take it to your shoe/luggage repair place and ask them to install/sew on support straps/rings so you can then carry it on. May help to bring an empty bag that has support straps/rings already installed as an example. My repair shop added them to my case for $15 - best investment ever.

David