by the book and the railroad we tend to model it calls for no more than a 3% grade and im limited to get to a 2.3% grade in a 17ft run.
I don't know what sort of prototype you are modeling. If it is logging or mining, the prototypes were not concerned with speed, and usually used switch backs to gain elevation without excessive grades. On Class one railroads, and most short lines the two methods for reducing grades are the helix and curves. The Tehachapie loop is a prototypical example of the use of a helix. Where the railroad curves and snakes it's way up a mountain is how they gain the necessary elevation without having too steep a grade.
What sort of equipment are you going to run; or, more appropriately, what is your minimum radius? The tightness of your minimum radius will determine how many "S" curves you can fit in a 13 foot long bench.
How much width is available to you for the bench work? A 4 foot wide bench would allow you to make longer "S" curves and get more footage in the 13 foot length. You can't reach the back of a 4 foot bench, so you don't make the front of the bench straight. You would have a "bump out" on the front of the bench wherever the the "S" curve came to the front of the bench, and a "walk in" wherever the curve goes to the back of the space. The idea is that the track should never be more than an arm's reach from the outside of the bench work. Where you have a "bump out", you can build an impressive mountain range behind the trains. Just don't put any track to the back where you can't reach it. Also as the elevation gains, your reach shortens. You can reach farther when the layout is at waist height than at shoulder height. At eye level, you will need a step stool to reach the back of even the narrowest bench if there is any scenery in front.