Sounds like your like me and keep your wallet in your front pocket, if it's the same pocket as your EDC a Diafold will probably be fighting for pocket space and be a bit uncomfy. I use my credit cards with money wrap around it with a rubber band instead of a wallet to keep the bulk down myself. But I find anything more than that and my EDC knife if it's clipped to the pocket will get annoying to carry.
If you try to keep the bulk down in your wallet I will assume the credit card sharpeners are out, I wouldn't carry it that way myself due to bulk anyway.
Though if you wear blue jeans the DMT mini's (not the keychain) should be able to fit into your watch pocket without issue. I would just cut up an old credit card (any plastic) to length and put it in front of the exposed grit to protect it from getting clogged and than throw a rubber band around it. The rubber band will serve 3 purposes to keep the stones together if your carrying F/EF, keep the protective shield you made attached, and add resistance to the stones so it doesn't fall out if you move around a lot. As for comfort I have put knives that are about 3.5in in length in that pocket and found it comfortable and forgot they were there (though I feel better with ones that have a clip in that pocket unless it fits all the way in or I use a rubber band). If you want to see if that be comfortable pick up a pack of trident gun will be close to the dimensions of 3 of the DMT mini's together but not as wide, carry it for a day and see how it feels.
I learned this trick since I EDC a traditional slipjoint a wear khakki pants which love to spill everything out of the pockets especially my phone and knife (only brand I found that fits my build sadly). When I attach the knife to my rubber band wallet it will stay securely in place and not budge once it falls to the bottom of my pocket. If I didn't use that rubber band I would have lost my knife, money, credit cards a million times over already.