Hard tops and roof racks generally do not have the load capacity to handle a roof top tent. The tents are not light... So I would be after a minmum 350 lbs rating.... That's heavy. I personally would want a heavier load capacity (like 400-450).
The MBRP rack looks sturdy but I would give them a call and confirm the load it can handle. Last thing you want is bend something. Also, as you said, you are drilling into the hard top. Extra weight will cause stress cracks in the top eventually.
Also... just be careful doing corners or off camber with it on... You are going to really be changing your center of gravity.