more than one at same time you cannot.
But you can just add more items to your list, and the only way to do this is to edit file items.cfg and to add the meshes in items folder, but doing this you can do mistakes and make the game to crash, i only recommend to do this for experienced membes.
Another thing to have in mind is the other people will not able to see your extra items, or they may see wrong items on you.
Ringo and Delays Item Pack is the most used and recommended for now.
But if you want i can make you a single item pack with Ringo and Delays Items and to add extra items to that pack, just put here the link to the item pack you wish to have in it.