[Plugin: WP Super Cache] existing .htaccess rules and supercache

I have some existing .htaccess rules to deal with backwards compatibility with older versions of my blog – in particular, I use a rewrite to match image URLs that used to be in the home directory to go to a new /images directory. Subsequent to installing WP2.8 + WP-super cache, this worked fine, but now it doesn’t (I just get a not found response). Is there something in the WP-supercache rules that is causing this to break?

Old rules (prior to WPSuperCache rules):

RewriteEngine On
RewriteBase /
RewriteRule ^([^/]*)\.pdf /docs/$1.pdf
RewriteRule ^([^/]*)\.jpg /images/$1.jpg
RewriteRule ^([^/]*)\.jpeg /images/$1.jpeg
RewriteRule ^([^/]*)\.png /images/$1.png

and WPSuperCache rules (afterwards):

# BEGIN WPSuperCache
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
AddDefaultCharset utf-8
RewriteCond %{REQUEST_URI} !^.*[^/]$
RewriteCond %{REQUEST_URI} !^.*//.*$
RewriteCond %{REQUEST_METHOD} !=POST
RewriteCond %{QUERY_STRING} !.*=.*
RewriteCond %{HTTP:Cookie} !^.*(comment_author_|wordpress|wp-postpass_).*$
RewriteCond %{HTTP:Accept-Encoding} gzip
RewriteCond %{DOCUMENT_ROOT}/home/realc/webapps/htdocs/wp-content/cache/supercache/%{HTTP_HOST}/$1/index.html.gz -f
RewriteRule ^(.*) /home/realc/webapps/htdocs/wp-content/cache/supercache/%{HTTP_HOST}/$1/index.html.gz [L]

RewriteCond %{REQUEST_URI} !^.*[^/]$
RewriteCond %{REQUEST_URI} !^.*//.*$
RewriteCond %{REQUEST_METHOD} !=POST
RewriteCond %{QUERY_STRING} !.*=.*
RewriteCond %{HTTP:Cookie} !^.*(comment_author_|wordpress|wp-postpass_).*$
RewriteCond %{DOCUMENT_ROOT}/home/realc/webapps/htdocs/wp-content/cache/supercache/%{HTTP_HOST}/$1/index.html -f
RewriteRule ^(.*) /home/realc/webapps/htdocs/wp-content/cache/supercache/%{HTTP_HOST}/$1/index.html [L]
</IfModule>
# END WPSuperCache

Any suggestions welcomed!