This is all getting very confusing
If you want to only use it for some posts, then you don't need the hack since you can do that anyway.
Also I figured the CSS out - with a little help from amykhar.
So, for anyone who prefers CSS sizes to HTML sizes
replace
PHP Code:
$message = "[color=".$bbuserinfo[post_color]."][font=".$bbuserinfo[post_font]."][size=".$bbuserinfo[post_size]."]".$message."[/size][/font][/color]";
with
PHP Code:
$message = "<font style=\"color:".$bbuserinfo[post_color]."; font-family:".$bbuserinfo[post_font]."; font-size: ".$bbuserinfo[post_size]." px;\">".$message."</font>";
You will also need to change the length of default_pcs and post_fontsize [Note: has to be in pixels or whatever CSS format you're using]