In general, not about the boat you linked from Dick's. That seems to have a huge cockpit.

More to kayak fit than just it's length and hull. It's more like buying shoes, since your legs have to fit under the deck and stay there. Nice if you can slide your legs in without having to sit on the back deck, kind of tippy like that. So test and see how long the opening needs to be. You can tell pretty quickly if it fits OK without getting it out on water. You'll probably still feel cramped up and need to get out every hour and walk around, but it gets better. Not like a canoe where you can move your legs around as you go. A higher deck in front will give you more room, but a less connected fit. Try used first, craigslist maybe. You'll probably be looking for something different after 1-2 years. Kayakers seem to change boats a lot. Course if you get a really cheap price you can always keep it for guests to use.