I would cut them back to the desired hieght you want them to stand at on the single branch to encourage a nice trunk with many off shoots:-)

If you want just a bare trunk with a canopy, then snip off the suckers that might start growing a few inches below the cut line, leaving an inch or two of growth to take off near the top of your cut line.

If you want it bushy from the soil level up, then leave the new growth that might come out from the soil level all along the trunk to the cut line at the top.

Mike