For Binary maps, there are instructions at the bottom of the README.txt document in the PK3 for setting up the chains. Basically, the ceiling height of the sector with a linedef of type 9 determines the maximum speed of the chain, while the y-distance of the linedef of type 9 determines the normal speed. In UDMF maps, both normal speed and maximum speed are arguments of the chain spawn object itself.
Admittedly, the value you need to use for the maximum speed isn't very clear. You need to take the value you would put for the normal speed and multiply it by 16 (ex. If your normal speed is 4 and you want a maximum speed of 16, multiply that maximum speed by 16, and use the result (256) as the actual value). If the value is too low, the player won't be able to speed up the chain.
I'll probably make an update to the README to make this more clear.