Replying to Yet another rail question

Ok so im building a 20 foot long flat bar that is  6 inches wide out of wood .. i was planing on just attaching PVC piping.. so i have a couple questions i need help on before i go any further.

1) what size pvc would work best for 6 inches wide

2) what do u think the best way to attach pvc pipe is
        A) drill a hole on top of the pvc and then put the screw threw that hole and drill threw the screw threw the bottom inside of the pvc

or

      B) drill the screws into the pvc by going threw the bottom of the wood base ( 2 inches deep) and up into the pvc

3) My hardware store only seels pvc pipe that is 10 maybe 15 feet long so how do u think i should go about the area where one pipe comes to an end and the other beggins. Do u think i should raise the up hill one a bit or what ?

4) Prob the worst question i have but whatever i  just wanna have fun with this new rail. But the question is how high do u think i should make this rail so its still fun but not to low to the ground?

Thanks NS and Build a Jib memebers +k