Some things that should be noted by those with a control panel:
Usually, there is some kind of SSH availability - check with the provided. The panels I've seen require you to use something like Secure CRT, generate the key, cut and paste the key into their web SSH interface AND provide the IP you are connected from (send yourself an email and check the header for your IP if you don't have a static IP) Your IP will most likely change each time you connect.
Anyhow, this will allow you to get to the directory on the host server where your domain resides and usually they install Smart List there. You can send command line strings from there. Charlie helped me a lot with that.
Additionally, although it's slower, if you aren't familiar with pico or the other Linux editors, rc.custom, rc.local..... can be edited from your file manager selection in the web control panel. Keep clicking on the domain, domain_mail, listname, etc until the files are shown. You can usually edit them from there and save them.
Hope this helps Liz