Sounds like you have some bear paws instead of hands!

I'm sure there are better ways more experienced smiths have worked out (I imagine there's a neat little ratio trick out there somewhere), but when I'm making or modifying for someone with much different proportions than me I refer to a couple of models I made. Really I just put some sculpey around a dowel rod, half harden it with a heat gun/blowdryer so that it's still moldable but provides some resistance, and have someone of similar portions to the person I'm building for grip it like a knife. I finish hardening it afterwards to preserve the model for later use. I have a small hand model, large hand model, and a "piano finger" model for my one friend who has absurdly long fingers. Sounds like you might need a medium hand model.

Then I use the appropriate model as a reference for sizing the handle. I can see where their fingers would approximately grip, where their hand would end, and I just compensate for that. If a particular flair for me is comfortable when it starts right where my pinky rests, I measure out where my model's pinky would rest and shape it there for instance.

Or just find a smaller-handed friend to help you test out a handle design and use that as a more finalized 3d reference from then on, if you're going to be making a lot of that same kind of handle.

I'm personally with you though, in that I don't care for flaring (or a lot of extra shaping of any kind to be honest). So if I'm building for myself I keep it super simple.

**Thinking about the ratio trick when I was typing this, and I suppose you can take a handle you find comfortable in the larger size and a piece of clear plexiglass to get a model made. Mark out the 4.5" on the plexiglass, and then place the glass between you and the handle at a distance where the handle visually fits right into the 4.5" marks you made on the glass. Then trace what you see, cut it out, and you have a 4.5" model. Like an artists' perspective trick I've seen used.

I was going to suggest that you handle them with your pinky extended. Then I remembered that much of the control is in the pinky.

So it will feel a little loose in the hand. However, I have a number of smallish knives (one is in my hand as I type this) and I noticed something.

If I hold this smaller knife with a handle that is 3.25" from the back of the guard to the front of the bird's head, I naturally hold it not cradled in my palm, but cradled in my fingers. My thumb naturally goes to the top of the guard and it becomes a very stable grip. With a larger knife, with a handle that is an inch longer, the handle naturally falls into the palm and my thumb wraps around it.

Perhaps you need to modify your grip on the knives, to feel how they behave.

Thanks, I got some ideas i will try out from the advice given.