You can use Metrix to output JDF to Trueflow which you can then use in truelflow. Biggest difference between working this way is that you need to create the whole imposition in Metrix, nit just one sheet which you can then copy. Metrix has a lot of nice features.
My personal recommendation though is to ask for your local Screen reseller to show you TF7 with Pre4m (or Equios as it is also called) this will have totally new imposition system, way better than Flatworker.