I find that most of my handles are 4.75" long. The balancing act is between making them long enough to work in the sabre grip and side pinch grip (skinning) without being too long when held in a full fist hammer grip (powerful wood carving). 4.5 to 5 is about right for most people's hands.
You sound like you design much the same way that I do. My first few knives heavily drew on Ed Fowler's work and later designs borrowed a lot from Alan Wood and Busse, which sounds a strange mix.
To design well, you need to use knives. Only then will you learn how what was on the page actually feels and works. To get yourself started, there is nothing wrong with drawing on the work of others, although a lot of folk like to see credit given when one maker copies another's style. It can be difficult to be original, and one shouldn't try to force it if you don't yet know what you are doing.
I knew a guy who was obsessed (okay, very focussed) on being original and not copying anyone else's work; he refused to read forums lest it polute his ideas, and he didn't want to learn from other's mistakes. He missed out on a lot and while his knives were creative, they were not terribly well designed for function or aesthetics nor well finished.
I would say that if you like the look of that knife, make it and see how you get on with it. At least make a rough prototype. I screwed up some early knives, went back and used car body filler to change the handle shapes and kept learning from them even though the heat treat was shot and the grinds were rubbish
Best of luck and welcome the forum.
Chris
