I have to agree with Alex, the wide ones do work best.
I've had a complaint of hair and skin balling up on the gut hook of one of my knives, so I've changed the design. I've widened the hook and am now sharpening up to the spine of the blade. This straight cutting edge cuts the hair and the top of the skin, especially when doing shoulder capes on larger animals like eland, kudu and gemsbuck where one has to cut through much thicker skin than the belly side. (The skin on the back of an eland can be up to one inch thick!)
To see an example check the art knife section of my knife catalogue on my website.
http://www.limpopo.co.za/burgerknives.htm
I drill a hole the size of the hook, then cut with a saw up to the edges of the drilled hole. The bevels are ground on a 1 inch wide 12 inch dia. contact wheel (this is quite tricky as you have to swing the blade almost 360 degrees), final shaping is done with a dremel tool, sharpening with wet and dry wrapped around a piece of steel rod.
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