Hi!
I wouldn't agree on the terrible timing part, RDShade is still a great tool for people using P3D V5 and the fact that we are currently not developing new tweaks doesn't mean the software can't be usefull (We still very much support the software and will release bug fix updates, only thing that we don't do is develop new tweaks).
To anwser your question, we have played around with this setting ourselfs and testing all different values, and going below 0.10 doesn't make a difference in-sim in our testing, going negative makes it darker again, so that's why we choose 0.10 as a minimum as unfortunatly that's the brightest we can make the cockpit's in V5 with TrueSky. It's very much a simulator limitation we have tried to correct as much as we could 🙂
I hope this anwsers your question, don't hesitate to ask more if needed, like I said, RDShade is still very much a supported product and bug fixes and updates will be released, however we currenly don't plan to put R&D Resources into RDShade for P3D due to the decline of P3D in the last year.
Kind regards