Had to google "bidon"...now I'm good.

Small frames, especially compact frames, can create challenges for water bottles...sorry...bidons. A guy I ride with has to use a smaller 20 oz bottle...sorry...bidon, on his downtube.

One option is to look at side loading bidon cages. It gives you more flexibility with where the bidon ends up in relationship to everything else.

p.s. Where in Austin do you live?