chlorine feeder advice

my local pool store only carries the 9lb inline feeder which seems big for my 5000 gallon above ground pool. is there any benefit or drawbacks to have this larger unit which i usually see advertised for in-ground pools compared to the 4.5lb unit. its a splash s168b. also, how important is using a check valve between this unit and the filter (Hayward EC40 DE)

It's a good idea to have a check valve between an inline feeder and the filter.

But why not just sidestep the whole question, and use a floater? For a 5,000 gallon pool a floater and an occasional dose of bleach should be fine.

PoolDoc