Change layers of multiple copper pour areas without loosing their net connections

I have created a total of 17 copper pour area shapes on the bottom layer, each of which is assigned a different net.

I want to be able to copy the same copper pour shapes onto the inner layers 'whilst maintaining their nets' (this is to increase the current carrying capacity of each net).  However, if I try to change the layer of ALL the shapes in one go, the nets assigned to each shape is lost because it assigns a new net.  

I will be using the same copper pour shapes on 6 inner layers, so its going to be very tedious to to change the layer of 17 copper pour shapes on 6 layers (that's 102 actions).  And if I change the design of the copper pour shapes then I have to do it all over again !

Is there an alternative method to overcome this ?

The process i used was to copy and paste the copper pour shapes.  It asks if I would like to 'Merge net with existing net' and I select 'All Yes'.

I then select ALL the pasted copper pour shapes (by windowing all the pasted shapes), right click and select properties and change the layer to an inner layer.  At this point all the existing merged nets are lost.  The only time the net is not lost is if I change the layer of each individual shape, but this is tedious and has to be repeated if the design is changed.

The copper pour shapes are shown in the image below:

It seems to be because I am using the Properties dialogue to change the layer.  With one shape selected the net name (SHUNT_-1) is shown in the properties box:

With all shapes selected the net names are not shown in the properties box (as expected) and this seems to be the reason why all the nets are replaced with automatically named nets:

The other method to change layers is to right click and select 'Change layer...' (or press the 'L' key) but this is not available when multiple shapes are selected.