The guards could go as big as:
Hall 6'4"
Demin 6'8"
Catchings 6'9"
Catchings will probably be a 4, but he could start at the 3 as well. We may not have the height at the big spots we did last year with Khalifa and Waterman, but Keita/Mag/Catchings are all much more athletic than those 2. That should definitely help with the perimeter D, especially with Mag and Saunders in there.
Last year our Guard line:
Hall 6'4"
Knell 6'5"
Johnson 6'5"