Andy,
the SLX lenses won´t work because their shutter and aperture is operated electronically. The 50/4 isn´t the best lens for macro. It has a poorer quality in the close focus range and if mounted reversed, it´s angle narrows somehow. It is right that HFT is most important with wide-angle lenses. For the longer lenses, the lens shade or the compendium are useful investments.
Greetz, Benjamin