I'm amazed that $ViewList[''] is valid php, but anyway, doesn't seemd to work. If the module only have one view, then you should look into using the singel function support.
HowTo: Avoid defining $ViewList, and just define the singel function in $Module['function'] like:
This technique allow to make compact module adresses by removing the second element in module's view uri.
But my exemple is not only for a "one view module" but to define a module "index" page...after $ViewList[''] you can add $ViewList['myview'].
The second benefit of defining this "empty" view is that people playing with their browser address won't arrive on a "undefined view" error when removing module's view name from the address.
I wasn't aware of your technique, i am gonna try it right away.
have you tried to use URL Translator in admin interface, and setup the following rule:
New URL alias: custom
Destination: custom/index and remeber to uncheck "Alias should redirect to its destination".
I use it in my custom module, in fact without any params, but i think it should work also with params. Maybe just you will have to use different alias name than your module... (not sure about it)