Replying to Need help on the dimensions of the drop in

Hey
I want to build a drop in tower so I can use it in the summer and winter.
Right now I have a 2 ft high, 12 foot long side by side pvc shotgun rail. It worked all right last winter with a snow drop in, but I think having a permanent fixed will be better.

I checked out the "how to build a summer setup" sticky and it was very informative, but I don't know what I should do to adjust the dimensions.

1) Is a 6 foot high tower high enough to get enough speed for a 2ft high rail?
2) If I increase the height of the tower, how much bigger should I make the transistion (its about 3 feet in the sticky)

any help is appreciated