Roof Top Tent and Roof Rails

[RoofRack]

I have an RTT on my 1999 and I'm concerned the weight is going to cause problems.

Does anyone know the strongest place to mount the towers? Is it a good idea to get a full rack to add rigidity?

 

[GhostRing]

Check this: 3rd Gen 4runner Roof Reinforcement
IMO probably don't need a full-length rack/platform, as it will likely just add extra weight to the already somewhat taxed roof. Certain crossbars will deflect less than others, but ultimately the integrity of the roof skin matters most.