From the first post it sounds like you connect the lower portion of the high camp bags to the frame like normal using the 2 3-bar sliders but I don't think you use the stay pocket on the high camp when you have the nomad. Bat wings and lid hold everything tight.
The more I look at the HC/nomad combo the more I like it. I picked up a HPG 25Cm bag and it works ok by its self on the bikini frame and I am sure it will pair great with the nomad. On the other hand, with the HC 4800 bag you would have almost twice the CI, compression straps, more than one access point and more options with another stand alone pack.