Open the .wav file in Edison (in the mixer), right-click on the sample-rate to the left, and a new window will pop up in which you can specify info, format, tempo and sampler details. You only need to alter "Beats" to 8. Now drag the .wav (using the icon in Edison second-furthest to the right) onto an empty Fruity Slicer channel. In Fruity Slicer you click "Slicing" and select 1/2 Beats. Voila! You now have a 2-bar loop chopped into 16 equal-sized slices. Each slice is obviously half a beat long.
Of course this method requires that you have pre-trimmed the .wav file down to ONLY contain the mentioned 2 bars (using, for example, Edison).
Peace.