oh
2240?
Xmax is a peak measurement,(if i remember right) and if you have a driver with 10mm xmax,with 20mm xmech, an 18MM mdf spacer should do the trick.if your sending it to its 20mm xmech then it will hit obviously,but thats what the xmech is-where the driver gets physically damaged.Purely arbitrary numbers there btw,i dont know the specs on that woofer.
you could always do 2 spacers..ofcourse that would increase the Front chamber volume.