I'd recommend not doing it in a Decath/ Citabria as they are really too easy to fly, and going from that into something less forgiving may bite you on the butt. I did mine in a Pawnee and am very glad of it.
Mattj, you are kidding aren't you?
I reckon the Pawnee is SO easy to fly that it probably shouldn't qualify as a tail-wheel endorsement.
I haven't flown the Citabria/Decathlon, but in a former life I did endorsement training in the PA18 Supercub - an excellent aircraft for ab initio tailwheel training IMHO!
Dr 
PS: For the record, I have time in Auster J1 and J5, PA25-150 and 235, PA18, C180 and C185.
PPS: Some time ago I posted the story of someone who tackled a C185 as their first taildragger - it ended in tears!