smartcard: transferring to another account

[Anonymous]

Hello,

I have a smart card with several keys.  All the keys are 2048 bits due
to the mentioned gnupg limitations.  All the keys are set up under unix
account 'A'.

I would like to use one of those keys under unix account 'b'.

I can export the public key, but clearly not the private key.  I have
imported the public key into the other account.

account 'B' can access the card, but I guess it is missing some type of
"stub" gnupg uses to mark the keys on the card?

How do I manually re-associate the secret key on the card with the
public key I imported?

I do not want to just copy the entire .gnupg directory over as there 
are secret keys I don't want exported.  

Again, do to driver issues, I apparently have no way to even list what
is on the card!

help?