Dimitar, I would suggest you use before the b&w develator a prebath - sodium carbonate 20 g / l. Time = 3 min. at room temperature.
I didn't follow your advice on that, since washing soda isn't so abundant here. I usually heat baking soda (sodium hydrogen carbonate) instead, but now I went in another route and tried HC-110 in order to avoid the fog. Well, it was a failure, since it didn't get the density right at first developer and the second dev just coloured all of the film in black.

My next attempt was to use LITH developer as a first dev and utilize it's insane contrast. Unfortunately my LITH is a local brew, unmarked, so if anyone wants to try it, my starting times will be useless.
So, in the LITH dilution destined for paper, I souped ORWO UT-18 (shot as 12ASA in the shadows) for 6 minutes at 20 deg. The contrast of the negative, needless to say, was insane, but probably my second dev. (diluted RA-4 for 5 minutes) was insufficient, and the final slide is really low in density. See the attached images. The crane was bright orange against a blue sky.