I configured NLB (aka WLBS) manually, and used a blpackage to take the node out of the cluster, update .Net Petshop to V1.2, and put it back into the cluster.
Worked like a charm!
I've not got it working yet, but adding
MS_WLBS = params.MS_WLBS
Got NLB installed, but I haven't got it configured just yet. (very close!)