The limit you refer to is a function of the settings under which PHP is installed on Dreamhost. As such, it is still set at 8MB.
While you cannot change that limit for the DH installed net2ftp installation, you can install your own copy of net2ftp (or other such program) and use a custom installation of PHP, or your own php.ini file with DH's installed PHP. to up the limit. Both processes are well described in the DH wiki.
You can also install a program with similar functionality written in perl, and thereby avoid this limitation (check hotscripts.com for lots of choices)