There is 3-screws in the end of the 211 lower clutch pulley that set the tension that it takes before it kicks out.When you look @ the pulley from the side you see them,to adjust it take out the short lock screw & turn the other screw in a couple of turns,do this to all 3.Then itwill take more force to kick it out you should be able to adjust your stitch,you might try (when holding the button down) turning the handwheel away from you this will make it shorter,towards you is longer.
The 211's all only have 1-button on the bed.