Redstone flux "intended" behaviour and how to fix it (Hopefuly)

[adamuso2I3]

Hello there, I wanted to ask. How do I add a JVM argument to the modpack that is through technic launcher. 
I need to add -Dcofh.rf.crashOnOldAPI=false
because of "intended" behavour of redstone flux.

Ideally before posting the modpack. - so you could download it and play right away,

I managed to do it in classic MC launcher and on server. But i have no idea how to do it here.
Thanks