Could someone give me some advise regarding leader and tippit lengths.

I'm having trouble getting my fly to roll out to the end like it ought.

The cast seems to just die about half way through the mid section of the leader.

I have a 4 weight weight forward floating line to which I've tied a 10 lbs. leader butt about 4 ft. long then a 6 lbs. mid section about 2 ft. then a 4lbs, tippit about 2 ft.

I'm tying them together using loops on the ends.

Any advice would be greatly appreciated.