[Spruce]

taken on board,
so spruce   it  wouldnt be any use  thinking about a 4040 or similar untill i tried to obtain more water pressure from my home tap first.
as you say a bigger booster pump will drain the water too fast. causing problems,      my pressure was around 23 / 25   very low for a big ro setup.

The other important issue is how much water you get from your tap when its fully open. If memory serves me a 4040 needs 7 - 8lpm to be safe. (I think Alex Gardiner had the correct info on his site, but the booster pump he supplied is no longer listed.)

A booster pump will increase the water pressure but if you don't have enough water coming into the r/o you will have issues.

[johnny bravo]

there may be a few lads with low pressure not knowing or even testing what it is.