rpm signing with subkeys

[Douglas Hubler <dhubler pingtel com>]

I cannot get rpm --addsign to work using a gpg subkey.  I added a key following
these instructions to my gpg key store: 
 http://ftp.debian.org/doc/gnupg/faq.html.gz#q4.14

And set this in my .rpmmacros
 %_signature gpg
 %_gpg_name 3455DDBA
 %_gpg_path /home/dhubler/gpg-auto

Where 3455DDBA is the id of my subkey, not my public key

And when I run 
 rpm --checksig my-package.rpm
I keep getting
 ... (GPG) NOT OK (MISSING KEYS: GPG#3455ddba) 

I've exported my public key and imported it to rpm,
  gpg --homedir . --armor --export engineering example com > \
     RPM-PGP-KEY-example.asc
  sudo rpm --import RPM-PGP-KEY-example.asc

Everything works find if I use the regular private/public key pair.

I discovered a macro by running "rpm --showrc" and experiemented with defining
  %__gpg_sign_cmd %{__gpg} --batch --no-verbose --no-armor --passphrase-fd 3
--no-secmem-warning --default-key "%{_gpg_name}" -sbo %{__signature_filename}
%{__plaintext_filename}

Where I replaced the system default fragement 
 "-u %{_gpg_name}" 
with 
 "--default-key "%{_gpg_name}"
but still no luck.

There are a lot of steps and I have gotten many of them wrong the first time at
various stages so even if you do not have advice for me, if anyone has ever got
this working, I'd appreciate an email saying you got it working would be
helpful, thanks.