Doing anything in HDV takes forever, including transcoding. I wouldn't recommend it unless you have a small amount of material.
One thing you can do to speed up your workdflow is edit as HDV but in your Sequence settings, under Render Control, select your render codec as ProRes instead of Same as Sequence. All your renders will be in ProRes now instead of HDV, and therefore take less time. FCP does, however, have to re-conform back to HDV on output but til then it works great.