If I am recalling what I've read correctly, if you want to train an SF you need higher potential because you are training a multitude of skills (assuming you want a good balanced one) so your SF won't pan out too well :s
Since all of them are tall, why not make them all bigs? It will be easier to train as well. I'd recommend lots of ID and IS training, then top it off with some REB. Their potentials aren't the best, so you won't be able to make too much out of them :s