That's a great idea! It is similar in concept to the altoids tin-compatible series that I made, except they are smaller. I presume that if you're making them credit card sized, then you plan to fit them into a wallet and will make them no thicker than 3.5mm.
Here are the challenges:
- TTF doesn't work. Essentially it shoots like a PFS with a pure OTT action
- The fork gap shape / tips need undercut to keep the bands on
- Flexibility and structural strength is an issue if you are using plastic credit cards
- Grip is a problem; you need a lanyard
- Sharp edges and protrusions may make for an uncomfortable grip
I will update these attachments later; I will experiment with a pinkie hole derivative.
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