Introducing new hens - too much space?

I recently got two new pol hens to add to my remaining two (age 4) and have read up about all the scenario's and realize this is not going to be a happy process (And noisy my poor neighbour's). We have had them since Saturday and at the moment we are letting them all out into the garden together and they are sticking together in their pairs. The newbies are not hiding from the old hens and will get close which is good so they are all aware of each other. One of the old hens stalk's the newbies and runs at them so they dash away from her they get the occasional peck which we are expecting. My question is are we giving them too much space should we lock them in the pen together and let them get on with it? Are we prolonging the process by giving them space?  The only real nastiness we had so far was last night on the perch when the stalker reached across the other older hen to attack the newbies and was quite vicious but I am going to have to lock them in pen together for a few days soon when I go to work and am worried so maybe I should lock them in now so I can keep eye on them? The top hen has jumped on another hen before and I'm worried if she does that to newbie she will damage them as shes a bluebelle so she's a hefty chook.  They can jump quite high so will have some where to escape in the pen. Any other advice to speed this process up gratefully received. Thank you

Give them space. They'll slowly sort things out, but you can't really speed up the process. One day you just realise that they are all mixed up together having a dustbath or planning world revolution.