Simple pot still 3" questions

[Spiritus Frumenti]

Hello all,

Newbie here and have been using a 2" column on a milk can for about 6 months now and just received a keg and want to build a simple pot still head. My friend has some 3" copper tubing that he is willing to give me, but my question is will i have any issues or will it be counterproductive to go from a 2" flange at the keg up to a 3" column? I've included my plans, but I'm also stuck on how big to make the liebig. Any advice would really help!

http://i1285.photobucket.com/albums/a58 ... 6b8a6d.png