5’8’’ - 310lbs - I have never been able to fit on the FOP test seat. The last time I tried, the CM told me to go through the line anyway and try the actual seat. I quickly found some tips online, and I was able to fit that time and every time since.
Here’s what I do:
1-sit down and move all the way forward; 2-(when the CM says they’re activating the restraints) sit up straight with perfect posture, hold in my stomach, arch my lower back inward, and lean forward;
3-(right after 2) lift my heels off the floor so only my toes are on the floor (flip flops or bendable sandals are best) and then relax my back and feet after the restraints lock;
4-if the CM comes to check my restraints, I repeat steps 2 and 3. Sometimes the CM has to push the restraints manually. Once the restraints are locked, I relax and experience the best ride ever!
My sister (who is larger than me) follows these tips, and she has been able to ride every time. We also do not wear thick or layered clothing on the ride. Hope this helps!