proxy_ftp : your opinion ? EPSV / PASV and firewalls

Hello,

Our firewall  between the proxy and the internet is configured very 
restrictive, so only known ports are allowed in either direction. This 
poses a problem with the EPSV/PASV implementation of the ftp proxy; 
servers that are able to run in EPSV or PASV mode make the proxy produce 
a "bad gateway" error ( Firewall / NAT ? ). I've temporarly enabled the 
bypass code but I was thinking of writing a more permanent patch.

Therefor, please your opinion: there are two ways to implement this :

1) add a directive to specify if EPSV and/or PASV should be used
2) alter the code to continue with PORT where it now throws a bad 
gateway error

The second option is the easiest for the administrator, but generates 
more processing overhead ( arbitrary ports will always be blocked, but 
the proxy will continue trying for every request ). The first options 
produces less overhead, but requires intervention by the administrator ( 
adaptation of docs, ... ).

Thanx !

Peter.