Here are my observations:
1) strips.jpg
a) Looking at the Dmax, density on the 100% step, it seems to me that perhaps you are not getting enough exposure, even at 8 minutes. The area where there is no OHP film, the right edge (I am assuming,) the density is measurably greater which means that longer exposure can potentially give still darker Dmax. I would do a strip of sensitized paper with clear OHP film on top and expose it in 2 minute intervals to see where the first two successive exposures are indiscernible. I do not know where the highest Dmax will fall, but as it is right now, I would say the print will look dull because the shadows will not be as dark as they can be in a Pt-Pd print. In that case, perhaps greater amount of sensitizer or double-coating might be required.
b) Looking at the Dmin, density on the 0% step, there seems to be some "staining" when you compare that step to the uncoated area on the edges, with lower one slightly darker than the top (not sure why, would have expected be other way around based on higher ink intensity) However, in my opinion, it still is fairly good so you can live with it if an improvement can not be made. I would try and see if the highest level 50 ink density makes any difference. If you were to print for longer time to get better Dmax, Dmin will suffer some more. Hence the need to use the best possible ink density, although it is limited by possibility of greater dot gain and loss of sharpness. A colorized negative will be the next possible avenue, assuming you are not already doing it. If all else fails, you can also experiment with adding higher amount of potassium chlorate solution.
2) grayscale_INT40.jpg
a) General observation is that the step matrix actually looks very good, given that no correction curve or gradient map have been applied yet. I only wish if my salt-print ones look as gentle as this.
b) With 2 min exposure, the Dmax has been reduced further, although not dramatically so, compared to the 8 minute exposure. However, the Dmin is now much better - nearly as white as the paper, judging from the edges. This is the trade-off. If you set the process with these conditions, you will have nice clean whites, but somewhat muted blacks.
Finally, both images you have chosen will be wonderful for the Pt-Pd, particularly the Calla. As would be many others on your website. Very beautiful work! I love the square format and the long exposures. (OT: I am looking for a good ND filter myself right now. Any suggestions?)
:Niranjan.