Howdy Nic
Got three ideas for you. This is my own personal edc and it's 5.25" oal. I'm about 6'4" with pretty big hands and this little guy has worked very well for me. I've carried this knife daily now for about 2 years or so. Has worked very well in my hands. This is my Vaquero Ultralite model.
Next up is the Gordo. It too is 5.25" oal. Prior to the Vaquero Ultralite one of these was my edc and I carried it for about 5 years. Nichole has one too and she has carried it daily for even longer. I agree that the curve downwards to the handle (as mentioned above) is very important in getting a design to work well in a large variety of hands.
Third is The California Coyote (in damascus, just the Coyote in AEB-L). This one runs 6.25" oal. I've been thinking I needed a new knife and have been contemplating making one of these for myself. I think the one thing that makes all three of these designs work is the downward curve of the handle. Seems to allow ya to hold on when there ain't much to hold onto. This one is my ranching partner's. its his edc and it has done a lot. I often accuse him of digging in the dirt with his knives. He don't really but fun to tease him.
Hope this helps, how is your chaps project going?