PVC Pipe Instrument - Could use a little help!

[Ryan Won]

So i've been creating a PVC Pipe instrument for a competition, which is based off the one on http://devices.natetrue.com/pvc/pvcphase1.htm
and similar to Rimbatunes created by Snubby J
I have many problems since this is my first time tackling a project this big. One problem i cant get think of how to fix is tuning. At first i though that when i cut tube lengths to match the certain frequency and some were flat or sharp, i thought i was simply off in my calculations. However over the past week i have noticed that much like organ pipes, the pitch changes with temperature. Im trying to find a solution as the weather at the competition site could be very different from where i am right now. I have one idea, which is to create some kind of extendable PVC length to add on the end of each pipe. However, i can't find any pvc that would fit inside each other that would let me create this telescopic length. Does anyone have any other ideas or a fix to the idea i have? Thank you so much ^^
Oh and if there is anyone with experience from PVC pipes, could they recommend what i should use for paddles? Im using sandles adn the sound quality isn't great.
P.S. If anyone wants it, i have data, failure analysis, etc that i can give to you. Also pictures if needed.

[Daniel Bingamon]

Tuning is simply achieved by cutting the instrument in half just below the blade top the top tonehole. A PVC coupler can be used to add to the length of the instrument. Simply slide it out and the tuning goes flat. Normally, the instrument is made slightly sharp so that you can always have a certain amount of tuning.

[Ryan Won]

However, for some of my higher pitched notes where the tube is very short, the coupling makes too much of a difference. Cutting the couplings themselves is hard for me because i don't have a high quality saw. I tried taping on a small piece of PVC but the sound quality audibly decreased.