Azure nested virtualisation recommendations


We are trying to move our packer/virtualbox builds off a bare metal server to Azure (which we build with Terraform as an aside) But the nested virtualisation is so far proving not to be feasible.

Our Windows base box we build (which is used by vagrant) takes about 5-6 hours to build on my laptop, but it timed out after 12 hours on Azure using an Standard_D8s_v3 instance.

Has anyone done this successfully? What Azure instance do you use and what is the multiplier you saw in time compared to building on bare metal?