[Lynne]

So, you want it so if users go to index.php, they get shown the forumid 4 forumdisplay page instead? Just leave forumdisplay.php and index.php alone and create a plugin like:
hook - global_bootstrap_init_start

PHP Code:

if (THIS_SCRIPT == 'forumdisplay') $_REQUEST['forumid'] = 4; //4 is the forumid I want to use. 


See if that does what you want.

Set index.php to go to forumdisplay.php (line 62) also.