I've never built a tube fin glider so this is just speculation.
Typically most high performance tube fin ROCKETS have the tube fin length approximately equal to or slightly less than the tube diameter. Ignore the Estes Super Neons and the Custom Razors. They work but that's all I can say about them.
My recommendation is to visit My.RocketReviews.com and do a search on "Larry Brand". He has done a lot of experimental research on tube fin rockets. I've had great success with cloning/copying his designs and did my Level 1 cert on his Sardo XXL design.
Tube fin ROCKETS have a very high coefficient of drag that is inversely speed dependent. The faster they go, the lower the drag. "Normal" rockets mostly have much lower Cd and no speed dependencies.
Kit (AKA Cranky Kong)
Total Total Impulse as BAR: 7,753.69 Ns (Equivalent to a 51% M motor.)
=| Calirado, Colofornia...what's the diff anymore? |=