Sorry if I missed the OP on this. Here are my thoughts, if it matters.
Yeah, the 17670s come in slightly different sizes (lengths). I use a different one for the prodigy than I do the GG. However the GG came with the "spacer" if you want to use 2, 3v batteries (length) & vape at 6V.
The spark plug is ok if it's your only mod.Let's face it, $25 for a tube mod that you can essentially vape at 3.7 OR 6V with! (I got the deal with the thermo tube). I've lightly, and I mean very lightly used it (3 times for a few minutes each just to TRY it out) and had switch problems the 3rd & last time I used it. It's not the "switch" inside, it's the coil that gets jammed up. I believe early on in this thread Ghetto Cowgirl posted photos of disassembling hers & stretching the coil back out. However, even after stretching out my coil & reassembling the switch it got pushed back down AGAIN.........so I had to repeat the process.
Yeah, the dime is "the poor man's spacer". However I've only used it in a battery charger, not inside of a mod. Technically a spacer SHOULD work inside of the mod, because it'll be making contact. Do not use a dime inside of the Spark Plug though. This will cause a double negative & will ground itself out (non working mod). A spacer is actually sorta like a battery (meaning that it has an outside casing aka condenser- so it'll conduct & fire properly. You COULD put some tape around a dime & then it'll work as a spacer in a mod.
I would throw my Spark Plug across the room in a heartbeat...........& definitely drop the extra cash on a mod that is not gonna cause you heartache. Let's face it, nobody wants to fiddle with a new mod! The new mod should vape, vape & vape some more. Pick up a used Prodigy for $75, or a GGTB at COV for less than $100, maybe an infinity for less than $100.
I do like the idea of a pencil eraser for the spark plug. That may be a good fix. I haven't used the spark plug besides that one night I tried it out, but maybe i'll give it a shot again tonight (i'm almost positive the coil is gonna get smashed down & difficult to fire), so i'll just rip an eraser off one of the kids' pencils.
I hate it when people are having problems with their new mods, but I enjoy the thinking process that I have to go through in order to assist in making them work.
FYI, for future reference in case anyone needs it............if your mod is metal, the outside body is negative and the batteries inside are positive. Therefore when the switch is pressed, you are putting positive to negative to create the circuit.
Good Luck! You'll get this going!