Perfect rail length?

It all depends on speed, but 6 feet is probably gonna be too short. What are you using it for? Summer setup or winter setup? How tall is your setup? What tricks do you want to be able to do on it? (if you reply with some of that I can give a better estimate, but..) For a summer setup, anywhere from 10-25 feet is good. On snow, 20-30 feet is better since you have more speed. However, the longest PVC you can buy at Lowe's or Home Depot is 10 feet, so my advice would be to make a 10 foot rail first and see how you like it. If you want more time on the rail, make another 10 foot rail and put them end to end for a 20 footer. If you have 2 10 footers you can also play around making elbow rails, A frame rails, down flat rails etc. so I'd recommend doing that.

Yeah I agree with what the above said. I would use 10 feet as a minimum. Rails seem longer until you approach them with skis/hit them. 8 feet sounds like a pretty long rail but in the snow it's pretty tiny.

That said if you're new to jibbing it might not be bad to have something smaller. Also if you're looking to try new tricks like 270s on etc, and want to come off the rail as soon as you land on it. That's a good place to have something small. Even if you come land a little off balance you'll be of the rail and riding away quickly.

The standard size for flat boxes a lot of places was 16' at one point. That's what falline and other places were building. Not super short, but not really that long either. If you hit it with speed you were off the end quickly.

Again as posted above making a couple 10' sections might not be bad. Could also do a 16-20'er and just drop the end farthest away from the lip down slightly, maybe a 1/4 inch depending on how solid the construction is so that you don't catch. In that cae it might not hurt to mark the top or bottom of the rail so you don't spin it around and hang up on it.

Good luck. Shred it!

I can get all eight on a 10ft rail. Anything more than one switch up/trick, your goin to need a longer one. Preferably 15-20ft

Personally I find learning on a 10-15ft rail that best 6 will probably be a little to short.