Here area  couple we built.  This one fits the 5140 and is the one that is hinged.  It is O.K. for loading trucks, but is kind of a pain for double stacking bales in the field.  I intend on putting  a lock of some sort on it.  It's really nice when stacking 3 high on trucks.

This is the other one we built at the same time that fits on Dad's Farmhand loader.

It doesn't hinge, and get's along fine.  The spears are from Agrisupply, and are their 39" forged and they have held up VERY well.  They are both made to safely handle bales two tall.  I would like to put an additional backstop on mine to handle bales 3 high, but, like you, I would have some shed issues, so, for now, just plan ahead.  As far as the side shift, when loading with a FWA it seems like you get enough movement to not need it that badly, although, once in a while, I'll push a load from the back to tighten it up.