ok......... a Reverse Osmosis system is normally a little hard-core, if your planning it for drinking water why not just use a carbon based filter as they shift most of the normally nasties in the water.
I mean i used a Empura filter tap supplied by Bristan and that did job easy and was very easy to fit.
It looks like a push fit to 3/8 adapter coming in to a 1/2 and thne in 15mm supply pipe, something similar to filters tap offer by just about everybody.
I Still think sticking a filter tap would be the easier way.