Ironically the worst kite for kite looping I tried was 2010 Slingshot Key 7m . That kite would loop 1 out of 3 times (if you are lucky). Other times it would just hit the water. And I used a bigger bar on it too!
Everything else I had looped just fine, including 17m Contra and about 20m Wind-X. They are slow and won't catch you in the air after a loop, but they won't hit the water.
Kites that fly at the edge of the window like crossbow need a bit of delay in timing to loop. If you are just learning or if you always want to stay on the safe side like me you want to go for helicopter loops. The idea is you have to turn the kite back ahead of 12 after a lift with the front hand just like for landing. So you rip along and you go for a jump. Now because you use the kite that flies at the edge of the window you have to send it more back beyond 12 to get a good yank and here is the delay to bring it back ahead of 12 to be able to do a safe helicopter loop. For the backrolls you want to stall the spin half way so you are in the air flying backwards keeping pressure with the front hand or just holding the bar with front hand so the kite returns forward of twelve then you turn your head to sort of reinitiate the spin while cranking with the back hand. If you do it right you wan't even feel the pressure on the bar. One more detail you need to keep the bar pulled in so the kite makes a tight turn which is against your instinct at first.