Another option is to make some nuc boxes to take standard frames and a further set of boxes the same length which will take the mini plus frames. The key is that your standard frame will govern the length of the box and the mini-plus will govern the width.
With these boxes you can get a box of mini frames drawn out, easily, on top of a 'standard' nuc; of course, the mp frames are running 'warm way' on top of the standard frames set up 'cold way' but it's not an issue for these units. It's also possible to use the same arrangement to get reserve store combs filled ready for use if the mini-plus' start to get light for some reason rather than feeding them direct. Just another option which does work well but is no better than the interlocking frame method.
I hadn't thought of this, thanks Rolande, another winter carpentry project beckons. I've already made a few nucs to take 4 mini plus frames cold way with a cut down milk carton at the end as a feeder, a la hivemakers design for half size national super frames.