Ronny Dahl has a good video on jacks - google will find it.
We had one for one "big trip" never had to use it so not much help I'm afraid. However it took up quite a lot of space and was quite heavy (didn't seem that heavy because the density is lower than that of a bottle jack. We sold it with the vehicle and now travel with two bottle jacks, which take up a lot less space, and can be stored a lot lower.