2.5" reflux column condenser questions

[Rooster351]

Well I am about 90% complete with my new still.
It is a 2.5" dia. offset column. Valved reflux. 46" long on top of a beer keg.
My condenser can is 4" dia. and I am wondering if anyone knows how much of a cooling coil I should plan on (length of copper).
I don't recall seeing anything to calculate how much to use. I will use a propane burner for heat.
I'm assuming more is better (as with most things).
I just guessed on my miniature version and it worked fine just was real slow. I'll probably do the same again but was just looking for suggestions from anyone that has run something close to this size column before.
I will probably be attaching this head to a real drum later on. Just because I can get one... It's all for fun...

Thanks for all the good info everyone has BTW. It's really helped on my small rig and learned a lot.