I'm exactly your size, and I can tell you that it's completely doable.... I have taken as tall as 6'4" and as heavy as 255# out of a 182. The harnesses are adjustable (I only jump Sigmas); you can jump 330's (I love our Hops 330s- very light toggle pressure). Really, it's so much fun, and if you really love and care about your students, the discomforts will be quite minor.
Laura Mullen
DZO, Santa Cruz Skydiving