A old article about the use of long stroke brake chambers and reasons for use, plus compatibility with automatic slack adjusters. * https://www.fleetowner.com/news/article/21659027/whats-new-in-slack-adjusters
Will add--Long stroke air chambers are commonly used with 8 5/8" wide brake shoes for added stopping ability. Standard shoe width is 7".
Im an little slow, but, a 30 chamber applies the same force regardless of the available stroke. That extra 1/2 of stroke doesn't push harder nor does it change the shoe to drum clearance when properly set. The only advantage I see is less chance of an OOS for overstroke. And overstroke means excess shoe to drum clearance. If your shoe to drum clearance is too large, brake application is slightly delayed, regardless of the chamber in use.
Correct---waited to see if anyone would note it. The reason/idea for long stroke is noted in this file from MGM. * https://mgmbrakes.com/files/6515/3055/8803/EB_02-002_REV2.pdf