When you reach the second half of the second rotation, extend your legs. Don't do it last minute

Try to concentrate and open your eyes to see how high you are when you finished your 1 flip. This will help you to get a better feeling and to land easier

If you don't do this already, get a double-bounce from a friend and then work your way down until you don't need it. It will just give you a little extra height and space to land it properly.

what worked for me was doing a full back arm circle before throwing the double front