proxy_redirect problems

[Sean Allen]

This might be simple and related to the fact that I have been working
way too many hours in the last 4 weeks.
If it is, please forgive.

We have:

rewrite ^/$ /admin;

which is then handled by:

    location /
    {
        index index.html index.htm;
        try_files $uri $uri/ @seaside;
        error_page 403 = @seaside;
    }

    location @seaside
    {
        proxy_pass http://gemstone;
    }

    upstream gemstone
    {
       server 127.0.0.1:8080;
    }

Urls after the first /

appear as

hostname/admin

want it to just be

hostname/

but cant get.

have tried:

   proxy_redirect  http://127.0.0.1:8080/admin/  /;
   proxy_redirect  http://gemstone:8080/admin/  /;
   proxy_redirect  http://gemstone/admin/  /;

and none work.

have done many times in the bygone days in apache but never
in nginx. can someone point out what i'm doing wrong?