Much obliged for the comments.

I followed the correct recipe for the FX-37 formula. All my chemicals are of good quality (analytical grade, if possible), and tested in other formulas.

Indeed I have no means to measure the negative density quantitatively. I just compare the negative with what I think prints as 'normal', devved in D.76. So my method is of a purely practical nature, but has always worked for me nonetheless.

I am beginning to think that the claims on the FX-37 speed enhancing properties are somewhat exaggerated. It's a good developer, nothing special though. I certainly prefer my good ol' D.76 for the tonal range and Gainer VC for speed and acutance.
From time to time I like to experiment a bit to expand my practical knowledge over unexplored territories.

Again, thanks for your input. I'm curious if someone has actually used the developer and maybe has similar observations. - T.K.