I've had precious cargo on our tandem (my stoker/wife) for over 34 years.
Never have had a need for triple or quads brakes in over 220,000 miles of tandeming.
We do live in hilly/mountainous terrain (Arizona desert is NOT flat!) and have tandemed in lotsa states.
Alloy rims and good brakes/brakepads + how you apply brakes is the best combination.