Quick preface, mod is working fine no isses there or anything, I appreciate you making this mod for sure!

I'm not sure if you are updating this anymore or not, but any chance you could add additional debuffs to the list?  Same kind of debuffs as the digigng speed penalty, but debuffs to:
Slower Mining, Slower Tree Chopping, and slower Scythe use.

Since hold something in your offhand would make those tasks quite a bit harder to do.

Markles The old cheater build should still work, it's like a single line of code.

Can you make a version that just removes it for the most recent version? <3

Removed the melee damage debuff as it was really annoying and negatively impacted the balance
(Enemies would take one extra hit to kill which would cost extra durability and unfairly nerfed sheilds)
The change should take place as soon as you put or take something off your offhand slot.

TimSithis
This isn't minecraft, it should just work.
If a version ever breaks, please post the first line of the stack trace so can quickly fix it.

Great mod, but Do you plan to update it?

OmegaHaxors ah, ok then.

Logically, you would think. But no, it's a translation error. It means Ranged Charge Speed. It charges 20% slower, I tested it.
Voidseeker

80% charge time means it draws faster, right?

Yeah, I saw the code

The mod sucks. It's a cheat mod that isn't even implemented properly. It runs the code constantly in an extremely inefficient manner.
This one's hooked up to the event handler, only runs when the offhand is updated, applies/removes the effect, and then that's it. Craluminum

There was also an old mod (link)