How stable is the ingentis? Worth looking at beefing up any rods or 4 rods for z axis or would that be TOO overkill because its rock-solid already?
I fear instability, coming from a Mendel 
I’d say it’s overkill. Think of the i3 design. 1 smooth rod on either side to hold the entire X gantry and that thing has a moving motor on it.
It wouldn’t hurt to use 12mm Z shafts and bearings. But not really necessary. Might be worth considering aluminium, hollow 10mm xy shafts to reduce moving weight.
@Tim_Rastall I’d be interested in seeing that work. I’d be too worried that the aluminum rods would bend, or wear away over time with the brass bushings over them.
The ones I have on my current printer (1/2 " PCB liner ceramic coated http://www.essentracomponents.com/sku/PBC-1052 ) work like a dream. But you can’t use roller bearings on them. They won’t flex. I will be using these on my ingentis variant potentially. But I will have to turn the ends down for the pulleys I just got in the group buy.