Mr. Malty's calculator does not account for "stepping up". I would suggest making a 1 L starter and then stepping that up to a 2L starter, then stepping up to 3L or 4L, you'd be fine. Hell, the 2L will probably be more than enough.
Making a light, low-alcohol beer as a starter will work great. Just make an easy batch and you've got some cheap beer with the wonderful benefit of a giant starter.
Making a light, low-alcohol beer as a starter will work great. Just make an easy batch and you've got some cheap beer with the wonderful benefit of a giant starter.