I've heard the dell support isn't great but here goes..
We're currently using 4 Wyse TX0's and connecting straight to a term server.. It's connecting using multiple monitors and they're spanning, we want to use the multiple monitors but in 'multimon' mode.. so the RDP knows there are 2 separate monitors and windows 'maximise' on only 1 screen at a time, instead of spanning across both of the screens..

If this isn't possible, please just say!! Thanks!