What i use is a 5' long piece of 2" Stainless Steel pipe. Place a piece of fleece on one send and clamp it on with a Stainless hose clamp. Fill the pipe 3/4 of the way up with activated carbon. Place the whole unit into the open end of a funnel to collect the vodka coming out of the fleece end and collect it into something glass preferably. Attach a very large funnel or siphon from a bucket into the open end and voila! The cleanest spirit you have ever tasted. If you need any help at all with the design, i can put up a couple pictures of my set up.
O, and make sure to run a little water through the carbon if its the first time you use it. you can use carbon over and over, but you have to clean it every 50-100L that you do. To clean the carbon, boil it in an old pot on the stove for 15 min. Then place the carbon on a cookie sheet with parchment paper. Bake in the oven for 1 hour at 250 Celsius for one hour with the oven door propped open. Keep a couple windows open. Can be smelly!
Have fun.
As for using plastic, try not to use too much. High alcohols, (anything above 30% or so), will make every piece of plastic very very brittle. Learned that the hard way. if you do use some, just remember to replace it every time you clean your carbon.