Kayak comes in different sizes so we don't want to give you an answer here without knowing too much details about your setup! Here's what we can tell you:
the rack is rated for 100 kg (220 lbs) - this is according to Tesla's official service manual
the production version of this rack is about 46 inches in length and 51 in in width
rack comes with 3 crossbars by default (but you can add more if you'd like); the crossbars have roughly 1.2in * 3.5in cross section and have standard slot for t-slot bolt that's 15 mm width (we will throw some t-slot nuts with the kit too)