As with any big spider, something I've started doing is providing a dual layer substrate system: Peat/vermiculite as a base (with a little sand mixed in for extra weight and cohesion if the spider is a big burrower) and then some jungle bark or repti-bark or similar orchid/bark/jungle mix with big chunks on the top to form a less 'saturated' layer to help prevent tarsal rot in the event the substrate gets too damp for whatever reason.
For a big parahybana, I'd suggest a broken flower pot or other structure to provide a retreat from light and/or prying eyes. It's a big deal for a spider to feel it has a refuge available - reduces stress. I've even used plastic 'big gulp' style cups and poured or molded peat and sphagnum moss over it to make it look more natural. Moss is fun for adding realism and can be another somewhat drier layer for a spider to hang out on as long as it's not saturated.