I'd like to reroute the outflow on my sump pump. Can I take the drain up 2', laterally 16', and up 2' more before it makes a u-turn and drains outside? If so, what additional horsepower might I need for the lateral stretch, and should I add a second check valve? Thanks.

You should have no problem with the distance and rise you propose. Almost any sump will push water that far with no problem. No need for a second check valve. You should be just fine.

Install 2nd check valve only if the discharge pipe starts "banging". Otherwise, MGD77 answered your question. Milo

Good call on the 2nd check valve Milo.