I have had quite a few makers make knives, usually of their own design or well established designs, to my specs. For instance, I've only had a few knives made by Scott Gossman, of my own design, I had no clue what I needed, only what I wanted. He still took my design and made a great knife. He also made a 3.5" bladed Kephart, with a slightly bigger handle, for an EDC blade. Other knives, he has made some for me with thicker or bigger handles, or variations on blade lengths. He doesn't take custom orders anymore though. I know what I want in a knife from him, and 99% of his blades fit my huge paws. Out of how many knives I have from him, only a few get really hard used, and they tend to be the smaller EDC/pocket blades.
I have ordered slipjoints from J Oeser, Dr T, Tracy LaRock, Gene Wiseman and I may be forgetting others. They used established patterns, Zulu for J and Doc, dogleg jack for Tracy and barlow from Gene. They used handle material I preferred, but the designs they used were already out there in the market.
Most makers are finding out that they need to stick with well established patterns. Whether their own or someone else's. I have traded into or bought second hand one offs from makers on the secondary market, and found it is very hard to trade or sell these knives. Well make knives, but not everyone is interested in them.
Many slipjoint and bushcraft knife makers will make you a knife based on one of their designs, with your tweaking the design. Before Scott stopped taking custom orders and switched to a store format, I asked him for his interpretation of a pukko, or later, a Hudson Bay camp knife. Feel them out. They like to play around on their own, finding out which designs work for them. The biggest part of the fun, other than using the knife, is thinking out the design with the maker. The makers I've worked with knew their stuff, and will tell you if a certain design doesn't work.
