axelant,
Like i have said I have knever flewn a stack but I have flewn blade's. If your just getting into this then i would reccomend the Blade II 4.9 its an awsome kite and you can get some seriouse air. Thats what I am personally into going huge on the beach. There is a ton of upward lift and in the right conditions you can get as much air as you want, you just have to be willing to fly in very high winds, probably near unsafe, but if you do you can have a ton of fun. I have gotten about 20 feet of air for about 7 seconds with the 4.9. Most fun that i have ever had.