You probably need more practice on your 3s. get them down perfectly. 3s are your base for learning bigger spins. if you can do a solid 3 with your knees tucked up and no back seat landing, a 5 should come really easily. if you're having trouble with the last 180, just make sure you keep your body compact through 450, dont open up at 3 like you normally would. same with 7, just hold the commitment, keep your body tucked up and your head looking for the landing. you can spot at 3, but dont open up your body. don't set too hard. you're not doing a double cork 12 here, 5s dont need to be set much harder than 3s, and as long as your on a big enough jump a 7 comes more from commitment in the air than setting the spin super hard, at least thats how i feel. check out trick tip or ask turpin cult, they know more than me