Gapping reeds for ease of overblow?

Groovy. I'll be here when you're ready Jim. In the meantime:

Tip: to determine the proper Gapping for your 6 Blow and 6 Draw reeds, I recommend you focus on your 6 Draw Reed first. This is the reed that will be doing all the heavy lifting.

1. remove cover plates
2. using diaphragmatic breathing and forward tongue positioning, blow into your 6 hole (exactly the same embochure as a normal 6 Draw 1/2 step Bend). While the 6 Blow reed is vibrating, abruptly cover the entire 6 Blow Reed Plate Slot with your index finger 
3. your 6 Draw reed should "pop" out-- sounding more like a squeal at first. This new note will be the flatted 3rd, exactly one octave higher than your #3 Draw 1/2 Step Bend (on a C harmonica this will be your middle Bb)
4. keep lowering the Gap (probably .003") on your 6 Draw reed until the OB note pops in effortlessly
5. next adjust your 6 Blow reed to a Gap (probably .003" ~ .004") that will allow you to generate the OB note without the need for your index finger. Be mindful not to lower the Gap too much because the 6 Blow is your middle octave root note and you don't want it to choke up on you!

Your HARPSMITH, Kinya