I tend to do simultaneous sammatha and satipatthana. I'll stay centred on the breath whilst simultaneously watching the sensations in my body arise and pass away.
However the (momentary) concentration on the sensations is kind of the inverse of the (fixed) concentration on the breath. I make it so that I have a kind of a leash on the breath. So I'm on the breath, then sensation comes up and my mind is catapulted into the sensation and then it springs back onto the breath. As soon as it reaches the breath another sensation happens...
I developed this by firstly getting on the breath then waiting for a sensation to arise. When the sensation arose I'd maintain awareness on the sensation and make sure it didn't spread out around the sensation (this way you are focusing on a tiny sensation which passes very quickly). As soon as it passed I'd ignore all other sensations and go back to the breath. When I was fully on it is was my cue to "listen" for the next sensation.
Now as this became more automatic I'd drop into the breath (far more than sammatha alone) and it would be as if the momentary concentration would be me looking through windows in the fixed concentration (the 2 were simultaneous).
The levels of clarity (coupled with a massively expanded periphery awareness) I got doing this were far surpassing what I got with straight sammatha.
So yeah - In my experience the periphery and centred concentration are inverses - you don't want to "look directly at" the distration (i.e. turn awareness towards it), you want to be simply retaining the awareness of the distraction as it comes into awareness if you get what I mean. The centred concentration on the other hand is develop by continually turning awareness towards the primary object.
If you can get to the point were you are getting the distraction as it's coming in, then try narrowing the focus of it (you can't "try" to do this - you'll miss the target and shoot out into darkness and it will hurt your head (well - that's what it did to me) - you've just got to do it (basically "think" - I'm going to do this and see if it then happens automatically after you've instructed your mind to do that).
Hope this helps.