[rack your brains]

You will in fact need to replace your factory rack on your 2004 GMC Envoy with a compatible and load rated base rack system that can handle kayaks transported on a kayak stacker carrier. The Yakima Control Towers & Base Pads Complete Roof Rack Base System is engineered to fit your '04 Envoy perfectly and is very quick to install. Using the set of Yakima Landing Pads #1 (included with Control Towers), the Control Tower multi-purpose base rack system connects directly to your factory rack tracks, replacing your factory rack with a compatible and load rated system for transporting your kayaks. Easy to follow instructions make the installation a snap (the Landing Pads simply snap into the factory rack tracks, no drilling required). The 58inch cross bars are the recommended length for your vehicle's rooftop and will provide enough room for carrying multiple kayaks on the kayak stacker.

The Yakima BigStack Kayak Stacker is the ideal option for transporting your kayaks and can carry up to four! Connects to the Control Tower base rack cross bars and transports the kayaks vertically on their sides. Easy loading and unloading too. Two heavy duty padded straps included. The BigStack Kayak Stacker is also designed to allow it to fold down flat when not in use, ideal for overcoming any clearance issues and also provides a more streamlined look when not carrying kayaks.