Penn 704z ?
 

Does anyone know or have drilled the rotor cup?
If so what size drill bit and how many holes?

1/4" hole in every slot

Remember that even though you drill holes in it so it will drain ,it is not sealed , so water will still get in through the shaft and the side plate.You will need to take it apart and clean/grease it if it goes into the water enough that you need to drain the rotor cup. Also since this is the time for big fish , a friendly reminder to take apart your drags -keeping careful track of the order of the washers , clean them good and get all that evil salt outta there! It builds up pretty fast even if you take good care of your reels.

And, don't try to drill thru the lead :humpty:

I went with 3/16 holes.Why?Don't really know,just did it that way.I also drilled a hole(1/32?) in each slot on either side of the lead counterweight.

And what Joe said.I had a ton of build up especially after fishing last week.