You are shooting about right. I think the IBO on a switchback is 316 fps you loose 10-12 fps per inch below 30". Plus a few items such as nock, loopand peep.Plus an extra 26 grains of weight per arrow.You would be about 65-70 fps below IBO approx 251fps. I would say you are doing good. My buddy's Switch back with a 27" draw and about 385gr arrows is shooting at 265fps. He has a drop away rest, maybe the whisker bisquit is slowing it down a few more fps
I haveseen many people boasting about how fast thier bows are and they are stunned when they shoot thru a chrono and it is no where near what they expected. My bow has an IBO of 333 fps and you can see my speed in my signature and that has been shot thru 2 different chronos.