I would venture to say the stock skid-plates are "satisfactory".
By this I mean when you're off-road, you are best to consider the OEM skids as "Early Warning Devices", and either back off or choose a new line to overcome an obstacle. When you feel that sudden jolt, or hear the initial screech on a rock, reconsider.
If you need a BIT more protection, consider welding angle-iron (I've used old bed-frame angle that I could find for free) as stiffening-ribs. Do this on the top-side, add some fresh paint, and it will look pretty good. With this improvement, you could probably get away with screech-dragging over modest obstacles. Beware: the transmission and transfer case remain exposed! I recommend covering these with aftermarket skidplates, or having a great pair of boots for when you have to hike home :lol:
However, if you're intent on dropping off rock ledges and landing on your skids, or bouncing and hopping your way up a a rock-waterfall, you'll want to look at something aftermarket, 1/4" thick or so. And probably carry spare axle-shafts. And a winch. But if you needed this much, I don't think you'd be posting here.
