I'll throw my 2c in this conversation, my JKU has aftermarket oil pan and EVAP skid, all else stock.
Only reason I put those skids on was because I took it to Moab new in 2010 had racked up less than 100 miles on the odometer.
Being bone stock, I hit the oil pan with bad lines, but not enough to cause it to leak. The skids basically became a panic buy at the vendor show but since then, I've not seen a scratch on either skid.
I'll admit I drank the kool-aid on the JLU after looking underneath and seeing how much more seemed exposed, I'm about to take it off and put the stock pieces back on.
As for the hitch skid, I run this bar in it to protect the tire; I know it's taken a beating on some ledges but no damage, not even with the JLU.
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