Depends on the make I would presume - the doughboy that Dennis recently installed looked to go about 3 feet deeper in the center, I have a normal J hook liner in my 30 foot pool and was able to go 8" without any issues - probably could have gone a foot or more, of course, you never know these things beforehand
Anyone selling expandable liners should be able to tell you exactly what you can do with it. Depth will be proportional to diameter I would think - 24 foot pool won't get as deep as a 30 with the same liner I'm thinking.