It's doable, I think. 2-minute ride time on the Shuttle, 2-minute ride time on the 1/2/3 (from Times Sq to Penn Station). That leaves 9 minutes of walking/transfer/waiting time. Bearing in mind the Shuttle departs pretty much every 2-3 minutes, and you can take any 1/2/3 train at Times Square, waiting time is probably shorter than you might think.

I think 13 minutes might be a little optimistic, but not much.