You can do what you want by creating a custom template fragment that enables proxypass on ".../extra"; the notes from
this forum discussion should help.
On my both my SME 7.5.1 and SME 8b6 systems I have a template fragment
/etc/e-smith/templates/etc/httpd/conf/httpd.conf/35ProxyPass that makes it look like you could do what you want using:
db accounts set extra ProxyPass
db accounts setprop extra Target http://192.168.1.35
db accounts setprop extra Description InternalServer
db accounts setprop extra HTTP on
db accounts setprop extra HTTPS on
db accounts setprop extra ValidFrom 80.90.100.0/24,74.125.93.105
expand-template /etc/httpd/conf/httpd.conf
sv t httpd-e-smith
(
set xxxx ProxyPass,
setprop xxxx Target http://<target> and
setprop xxxx Description <description> are required; all other lines are optional)
* I can't find any docs in the wiki on this
* It doesn't look like these directives are going to work for HTTPS connections by default (they end up inside a "Listen 0.0.0.0:80" section in httpd.conf), but I'm no expert on httpd.conf.
From my digging, it looks like
35ProxyPass is old (mentioned in a bug from 2006), while ProxyPass SSL support was fixed in a later bug (in 2007), by which time the ProxyPass code had been moved to the virtual domains templates.