My two rows are at the exact distances you discuss and I have a 49" tall CIH screen. That is as big as I personally want to go with the first row at 9.5'. For me, the limiting factor is the quality of your source material. If everything was 4K or even blu-ray, you could go taller, but a lot of things I watch (like HGTV off of cable) are just within the acceptable image quality range for that screen size/seating position combination. And for things like 2.35:1 content from TCM (Turner Classic Movie channel), I frequently just letterbox within the 16:9 region rather than zooming it out to use my full screen because the quality of the source is so bad.
I have a JVC 4910 projector and a Stewart Cima Neve 115" wide x 49" tall screen. The surrounding front wall and the first six feet of the ceiling, side walls, and floor are all black in my theater.