Ello and welcome. If you can post a lil vid ( from a 'phone will do) of what you can do/trying to do. It may just be a little of your style that needs 'tweeking'.
To get the height you need to put all your wieght directly down onto the springs. This means, jumping thru the heels, keeping a str8 back and looking str8 ahead ( or looking down about 4m or 12 feet ahead).