And, from my experience, this is not worth reconstructing an aligned model by chunks on seperate computers, because there is a “fixed price” (the depth map computation) that means that you would have to do it several times on each computer.
Just try to reconstruct the whole model on the bigger machine that you have (CPU/RAM/GPU).
Once again, it depends on the case, (and this is only my experience) but working with high res 42MP I never reconstruct at downscale 1 (high), except for small objects scanning. Depending on the case, I am usually working in D2 or, sometimes, in D3 on big projects (like more than 20,000 pictures reconstructions). The 42 MP become really useful when you texture - and at the end, I am simplifying my 1 to 2 Billions triangles model to something more manageable in the millions, so, sometimes no need to aim for a too high reconstruction quality.