2nd Gen Tundra Towing Question. 2007 Double Cab 5.7L w Tow Pckg

2007 Double Cab Platinum 5.7L V8 4x4 TRD Tow Package; 123000 miles
Toyota says my max tow capacity is 10,300, and I believe tongue max is about 990 lbs.

We're looking at tow-behind trailers in the 5000-5800 dry weight range, which should put us up to around 7500-8000 loaded. Many recommend staying at 80% of max capacity or below.

What's your experience?
Should I consider a transmission cooler?
5000 lb air bags?
Other?
Or is it still a bit undersized?

A friend has a 2016 Ford 150 with an 11,000 lb tow capacity and a 29' trailer that is about 5000 lbs dry. He's fully within weight limits. He had issues going downhill with the trailer; brakes not working that well.... not sure if he didn't adjust his trailer brakes correctly.
He also had issues on winding mt roads where the Ford just didn't seem to have the torque to keep it going fast enough, and he was pulling over all the time to let people pass.

Suggestions? Experience?

 

If it's an 07 tow package, the transmission cooler is already there. I'm no expert, but depending on the climb and decent grade even big rigs struggle. Not sure about the F150, but I've used the engine brake to slow down out of the Sierras over my brakes. I haven't towed up to the max of 10,700, closes I got was probably 7k.

 

thx for the input. I have noticed that the Engine braking when in manual gearing if very strong on steep downhills, so that is a good point to consider.