How do you make a tube out of sheet styrene?

[Unreality]

OK, so I'm trying to scratchbuild a Hoth Golan Arms Df.9 battery (the big white turret). I'm trying to build the center tube piece. I've measured everything out. The bottom diameter is 7.1 cm, top diameter is 6.9 cm, and the height is 7 cm. Is there a pattern for laying this out on sheet styrene so I can cut it out and curve it into the tube I need with those dimensions?

Any help is greatly appreciated!

 

[Grendels]

The only thing I can think of is to take and cut out a few circles of the right size and using them as an internal brace so that the tube will take the proper shape.

 

[Unreality]

Thanks.

A friend at Keeper of the Force posted a link for a truncated cone calculator: http://www.templatemaker.nl/index.php?template=cone&lang=en

 

[LrdSatyr8]

I was just gonna post that same link! That comes in soooooooooooooooooooooo handy for making cones with odd sizes!