Bottle jacks not the best choice.. They tend to leak and if you will pardon the expression "let you down" over time.
Better choice is a bottle jack (or two) and a set of jack stands.
jack up too high, lower onto jack stand.. Or bottle jack (Cause it's easier to lift with one) and a screw jack (Solid for just the job you want by RV stores)
Many RV stores sell a stackable stabilizer.. Consists of a frame like a jack stand farme with a bolt and nut and pad and some stuff. Will try to find link on CW.
Note that the jack I link to may be too tall for your use, They come in diffent sizes but I'm mostly in giving you a look at 'em.
Stacker Jacks