For a CA-2 take a look at the T-Cycle mount
Zach Kaplan in Alameda has a recumbent/trike shop, has experience on many bikes (including Bacchettas), and extensive long distance experience:
It really does vary based on the bike. For my P-38 I varied the light position between the handlebars (but you end up with "foot flashes" as you pedal) and the front derailleur post. I've mostly kept the lights in front of the cranks (Metaphysic, M5CHR, and Cruzbike S40) with various ease -- the S40 has a handy tab that you can bolt a Paul Comp "Gino Light Mount" to, and the others I bodged together parts to mount to the derailleur post.
Because the light is now fixed to the bike (except in the S40 case, where it flops around with the steering), I always use a separate headlamp that can cycle between low/medium/high that I use to illuminate the bike computer on low, set to medium to read street signs, and high for bombing down hills. And it's good for flashing cars to make sure they're aware of you.
Whatever you do, test all of your lights well before any ride you'll depend on them.
And congrats on your randonneuring to date. I'm the one who introduced myself at Dillon Beach. I took my road bike that day due to the climb out. And yesterday I saw you at the start, though again I was on my road bike, so I couldn't commiserate. :-) I'll be doing a few of the upcoming rides (Santa Cruz and Davis) on recumbents, so hope to see you out there.