So, A<->B is SSL and A<->C is shared key, you're running two separate instances of OpenVPN on A?
While there's nothing inherently wrong with that (I run many instances of servers and clients on my boxes) is there any reason not to consolidate the connections into a single server on "A"?
If you've already "bit the bullet" and setup an SSL instance, I would suggest making both your connections SSL.
Even if you need two separate instances, it'd be worth making both SSL IMHO.
While getting the routing options to work with Shared Key is possible, I've always found the options more limiting compared to SSL.
Pretty much fill in the network lists you need on the Server side, add the CSO's and you're up and running.
The other plus would be we don't have to debug two types of connection (that's just me being greedy ;D )