IIS 7.5 + CGI + SSL - How to increase the upload limit?

I'm hitting a really annoying problem with IIS 7. I've setup my web.config by the books as follows:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <handlers>
            <add name="Python" path="*.cgi" verb="*" modules="CgiModule" scriptProcessor="C:\Python27\python.exe -u &quot;%s&quot;" resourceType="Unspecified" requireAccess="Script" />
        </handlers>
        <security>
            <requestFiltering>
                <!-- maxAllowedContentLength is in bytes (B)  -->
                <requestLimits maxAllowedContentLength="1073741824" /> <!-- 1GB -->
            </requestFiltering>
        </security>
        <rewrite>
            <rules>
                <rule name="rewrite to hgwebdir" patternSyntax="Wildcard">
                    <match url="*" />
                    <conditions logicalGrouping="MatchAll" trackAllCaptures="false">
                        <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
                    </conditions>
                    <action type="Rewrite" url="hgweb.cgi/{R:1}" />
                </rule>
            </rules>
        </rewrite>
    </system.webServer>
    <system.web>
        <!-- maxRequestLength is in kilobytes (KB)  -->
        <httpRuntime maxRequestLength="1048576" /> <!-- 1GB -->
    </system.web>
</configuration>

When I POST to the CGI script (it's hgweb for Mercurial via Python) via HTTP everything is fine - no problems whatsoever.

However, when I POST to the script via HTTPS (SSL) I'm still capped at the default upload limit of 30MB. This doesn't make any sense to me. What is going on?!