Not a climber but I've set one of my road bikes as 1x and I run 44x12-36. I think you can get away with 42-48t up front and still be respectable on the flats. No 48t for me though as I can't really big-ring up all of the local hills with my 50t double. My 44/36 is like a 34/28 and I've considered going down to a 42t up front to get a slightly lower climbing gear (still running 10sp so 11-40t cassettes have too much gap in my opinion).