Hello, im going to start the upper lower split 2x a week workouts and im wondering several things. im wanting to add in a arm day on Saturdays basically because I look forward to it on my day off from work and I have good arms and I want them to stay that way. is that ok for my goals? also I have a home gym i dont have a leg curl or leg extension machine how and is it ok to substitute? possibly sissy squats for leg extensions and rdls for leg curls.