A couple of inches might not be necessary but every inch will help. My guess is that because your tube sits so high it may be catching some of the air that sits in the scupper hole.



This is what mine looks like

https://lh4.googleusercontent.com/-c...-no/15%2B-%2B2

https://lh6.googleusercontent.com/-_...-no/15%2B-%2B1

Thanks guys! I'll extend my tube a little bit and hopefully that will solve my problem!

Sounds like you eliminated everything else, glad to hear you got the problem solved without spending any money!