Just a little correction- right now Walmart's Relion insulins are Novolin R, Novolin N, and Novolin 70/30.
My personal experience is that I need less than a 15 minute prebolus and more than that is a problem, with Novolin R. But that's me. I also sometimes break my mean up (about three quarters, one quarter) and eat the second part of it 2-3 hours later. Particularly for breakfast.