I would obtain the spec sheets and determine it for yourself. I use a rather large array to mount my 30" monitors. But I mount them vertically.... and I use the regular DS 100 (no extension arms) for most of it due to the size of the 30"s.

The bottom line is that I don't exactly follow their suggestions as to how to put this together. But if you know what you are doing - it is a very adaptive system.

I don't see why you could not mount a 24" and then a 17" above it though if you pole mounted them then clamped it to your desk. That should not be a problem at all. Just get the pole to VESA mount part and clamp away. Make sure your pole is high enough though. If they don't sell them, I suggest onlinemetals.com. Be sure to get 1.5" OD TUBE not pipe. If you want to look factory, take it to a local powder coating place.