Yes, those seats could be tricky! Many years ago, during my time on the Loop, I was fortunate to fire for many of the "old heads" that had retired in the late sixties and early seventies. One of these gentleman was named Charles (Charlie) Rumph.
Now Charlie would also use the window ledge as a seat going up or down the hill, but as the day wore on, so did Charlie and he would flip the seat up and use it on the up-hill trip. Now for some reason, somewhere around the high fill, Carlie would have to make an adjustment with his legs and "WHAM"! down he would go as he kicked the support bar out from under the seat. Poor Charlie would hang on to the throtle for dear life (pulling it wide open) and would get wedged between the seat and johnson bar quadrant and couldn't get up. I would set the firing valve the best I could, cross over to the other side of the engine, shut down the throttle and help poor Charlie out of his prediciment. The poor guy would be cussing up a storm, embarrassed, etc. By the time we arrived at Silver Plume, he was so discusted with himself that he would have me run and he would fire for awhile. Charlie would calm down, enjoy the trip down the hill and get the fire set for the return trip. Once we got going, he would flip up the firemans side seat and settle in for a relaxing trip up the hill. Pretty soon (just as I expected) somewhere around the high fill "WHAM" Ahhh!@#$%^&*! Big inky clouds of black smoke were pooring out the stack as Charlie held on to the firing valve this time (pulling it wide open) as he fell to the floor. I would set the throttle, cross over to the firemans side of the cab, get the firing valve set and help poor Charlie up. Poor guy, he did this to himself more than once during my day. He was effecient with this manuver on either the 40 or 44 as well!