You could stub up with pvc and put a coupling so that the top is flush with the bottom of the transformer. Then you could use an adapter like the one pictured on page 15. You would not have to lift over threads and risk damaging them. Just shimmy the unit to line up the knock-out that you had made and slide the adapter on. Low profile and allows immediate bending if conductors.
http://www.beckmfg.com/pricesheets/pvc082.pdf
