I was changing the rubbers today on my World Fair and was actually struggling on a couple of them. Especially on one where the screw had to go thru a plastic and then a lane guide and then thru a 2 piece metal post, and the ring was under the plastic going over to another 2 piece post, also under the plastic. It definitely was trying my patience. I could easily have used at least 3 hands, and this was just a simple EM. It got me thinking that on the newer machines that there has to be even harder ones with all the ramps etc. What is the hardest one that you have ever come across? And how long did it take you?