personally, seems like the 9-10% range is where things get...interesting. yes you can stay seated leaning forwards because, if you don't, the front wheel tends to "lift off."

hopefuly, the climb is short/shortish and you can grind through it. if it is longer and/or steeper, will likely require multiple applications of seated, leaning forwards and grinding at 3-6 mph along with a healthy dose of out of the saddle for a 50 count here and there.