Hi, when you reobfuscate your mod, can you use reobfuscate_srg.sh/bat instead of the one without _srg please? This would give it some chance of running on 1.6.4 - worked for my mod, anyway.
But of course, it won't resolve these IC2 API problems in experimental. That's to be expected, though.
Cheers if you do, loving the mod a lot, played it pretty much since it came out.