Will you be using the cisco vpn client on the PC? Or will you be using the IPSec code that comes with the OS, or someother client?
How was you dynamic crypto map defined? If you still had the the 10.50 peer defined in that map then it does not matter that the map is definec dynamic, only that 10.50 peer can connect. Normally dynamic maps are used when you do not know the peer beforehand. You could modify the isakmp key to only be used by the 172.17.x.x subnet instead of anyone, to insure that general internet hosts cannot try to connect to your pix via IPSec. You still should not define the set peer in the crypto map though.
Let me know if this helps and whether or not you need more help.