not sure if this is any use to you, but I do piggy back my Topas cases if you have a look at this image on my instagram feed (wasn't sure how to embed the image in this post)
http://instagram.com/p/c4Ry_1pkiS/
In this I have a Rimowa Topas Multiwheel 70cm, with the IATA Cabin multiwheel piggybacked on the back and a delsey laptop bag sat on top, using the straps on the front of the rimowa cases I guess you can configure and link multiple cases.