Hi,
I used cobiax technology sometimes, also with good results in comparison with the calculation report of cobiax engineers.
I've done this way:
1) I've defined a new concrete material, with self weigth reduced. This reduction depend by the dimensions and density of the bubbles;
2) I've applied to the floor panel (slab) the inertia reduction coefficient. Usually in cobiax technology the reduction coefficient is about 0,88-0,92. For the definition of the right reduction inertia coeff. I have an excel spreadsheet, unfortunately is in Italian. Cobiax engineers give me this spreadsheet, if you don't have it, try to request to your local cobiax engineers. Let me know if they don't have...
3) take care to model correctly the unbubled zones for punching with a slab that have the full inertia and the full selfweight.
This way you can model the slab correctly and calculate the required and provided reinforcement.
At the end take care to share your results (reinforcements, deflections an so on) with cobiax engineers for comparison.
Hope I help you, cheers.

PasProStudio
www.pasquiniprogetti.eu
Structural + Detailing engineers