Sysex negative values - help needed

I’m almost finished with a Guru definition for the KingKorg synthesizer, but have been defeated by the changes in the sysex string caused by bipolar parameters:

For example:

Velocity Sensitivity positive values is:

F0, 42, 30, 00, 01, 18, 41, 02, 00, “25”, 00, “vv”, 00, 00, F7

whereas for negative values the second and third last bits change to:

F0, 42, 30, 00, 01, 18, 41, 02, 00, “25”, 00, “vv”, 7F, 7F, F7

I’ve tried all sorts of guessed combinations of coding to make it work so that the slider will go from -63 to +63 but without success. I’ve done a lot of internet trawling as well and can see other people solving this problem with other hardware in other software.

I’m wondering if I need some sort of - if, then, else- combination, or do I just need a value name and number for the second last two bits - the manual calls them “vvm” and “vvh”, but if I put them in the string it doesn’t work at all. Any idea of what code or otherwise I need for this would be massively appreciated.

By the way, there is a complete absence of KingKorg software editors on the net, so maybe this would bring more people to Renoise, currently in its 95% finished state this definition really opens up the synth, and to be able to randomise all settings is pretty amazing.

Thanks for any help.

I guess this question is Guru-specific?

You might have a better chance of getting it answered if you post in the guru topic over here

thanks danoise, I have done what you suggested