In the meantime, four flowers have opened. And I guess there will be a few more.
Years ago I used Pentax cameras and had a SMC DFA 100 mm macro lens as well. Except for that and the Pentax FA77, I sold everything all Pentax gear. Even back then I was not too happy with the DFA100.
Stopped down to f/16 and beyond, extreme diffraction kicks in and with an open aperture, circles of confusion can sometimes look very strange. Eventually chromatic aberration plays a trick upon the bokeh. I never got really warm with this lens.
So why not just use a proper aperture of f/5.6 and then combine multiple exposures using focus stacking. When changing the focus, the lens breathes quite a bit and the angle of view changes drastically. And since I don't have a macro slide (yet), I would have to adjust the focus instead of changing the distance of the camera to the subject.