I thought I would see what I could do with my home-made HMC set-up. By home made I mean that both the insert in the condenser and that in the objective have been fabricated by me, quite simply with fairly basic materials. I realise that it is not ideal, and needs some tinkering with, but then that is part of the enjoyment.
Unfortunately, I read the name Gyrosigma in the text of a comment, and quite missed the fact that I think the sigmoidal frustule in the original shot is Pleurosigma. Hopefully it still illustrates if it works OK.
Nice! Have you described your home-made HMC setup somewhere? Since I am going to build my own HMC condenser, I'd love to see it and get some ideas. I'm impressed you built your own objective, too. Was it difficult to get the modulator at the correct position at the objective's back focal plane? I know Leica has a system where the modulator sits outside the objective (Leica Integrated Modulation Contrast), but I would guess that that is only possible with infinity corrected optics.