What size cord can you stuff in there? I wondered when purchasing. Measuring width across the brass extender threads with a cheap brass caliper... they range from 1/16"-1/8" or 2-3.5mm - Again, this is width, not thread size. 'tad' in this context is <= 1 layer of masking tape.
The paddle is solid and threaded but has no extender.
The case: The leather is very soft, supple even. It is high quality and well made. I pulled and twisted to see if it would tear. It did not. In fact, the case shows no ill effects at all. Very nice, indeed.