Re: Bolts -- I was thinking mostly in terms of distributing the heavy load more evenly to the chassis, though it probably came across as focused on tongue weight, which I doubt benefits as much from that. I've got to believe there are very good reasons why Toyota engineers designed the OEM hitch the way they did, and one would think it would be in support of the max towing capacity available for the model more than anything. Overkill on an I4, though.
I *think* I remember reading somewhere that there were some extra mounting points for a hitch in front of the rear bumper with the Tow Prep package installed as well. Though I don't remember where I read that. I think it was pitched as a way to tell if you have the Tow Prep package, though looking for the 140 Amp fuse under the hood is almost certainly easier.
For the I4 in this case, I'd also be very
worried about the transmission overheating. I think one of the things the Tow Prep package offers on the V6 is a bigger radiator for better transmission fluid cooling (see here
I wouldn't be surprised if that were the thing that most contributed to the boost from 2000 lbs towing capacity to 3500 lbs towing capacity (that, and an upgraded fan coupling), as the rest of the Tow Prep package appears to be just a bigger alternator and possibly some pre-wiring through the firewall to assist with hooking up the trailer lights.
Apparently the I4 has a small tranny cooler (see here
) but my guess is that it's to get the towing capacity up to 1500 lbs to begin with.
As such, I still wouldn't even think
of trying to tow 2700 lbs minimum with any North American petrol I4 RAV4, unless it was all downhill.