Drag on the rod is directly proportional to lug surface area contact with the rod.
Since 1/4" has more contact area than a 3/16" lug, given same rod/lug material, drag will be higher.
I dont know of anyone selling launch rods with a few threads at one end. You could cut them yourself if you have a die set.
Use STAINLESS rod. Trust me on this.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !