I'm about your size (although I already dropped the weight after the baby :) ), and I LOVE my 18" Thornhill Vienna, 32 tree. I have TB-like-built paint and it fits her nicely, I also used it on WB during the lessons this year, and it also was a nice fit.
Passiers are nice and comfortable saddles too (but I never rode in one, just sat).
Stubben was one of the worst fit for both of my horses (all models I tried).
"Life isn't about waiting for the storm to pass: it's about learning to dance in the rain..."
"When we are no longer able to change a situation - we are challenged to change ourselves."
"How people treat you is their karma; how you react is yours."