Looking at the Copper Rails recipe it seems incredibly over powered when you consider normal powered rails.
For example gold is a lot harder to find than copper yet the copper rails are technically better as you can power them up to 100 blocks instead of 8.

I'm wondering if it's possible to add in a debuff of some kind that makes it actually worth crafting ordinary powered rails again. For e.g. as the rails oxidise they get slower and need to be waxed to stop this happening.

Suggestions for debuffs:

- Make it so they oxidise, each oxidation state reduces the top speed by about 10%. Rails can be waxed to stop this from happening
- Hook a Mixin into the gold powered rails code and make them slightly faster, for e.g. by 20% to compensate. Would be helpful because Minecarts are super slow already

I like your suggestion. I don't wanna mess with the vanilla rails, so I'll probably make the copper ones oxidize. Though I'll have to look it over before implementing this and probably make it a config option.