A few questions for stompbox loopers

["Gareth Hardwick" <gareth@olympia50.freeserve.co.uk>]

I've got a few questions for those of you who use stompbox loopers,
particularly people who use two or more in their signal chan.

How are they placed in the signal chain? For example are they run in series
(one looper after another), or parrallel (using an AB box/line selector)?
Is one looper placed before or after any particular effect in their signal
chain?

I'm asking because i'm currently running two loopers (either a Boss DD-20,
DD-6 or RC-20, depending on my mood) in series and i'm curious on whether
their positions in my line of effects pedals is making the best use of 
them.

Thanks in advance!

Gareth