ive seen similar, some people add material to the front of the bow to fill out the grip area. sorta like your idea. the grip you show their seems like it would help set your wrist angle if the part of the handle that extended out the front was toward the top limb. you can add layers of leather to the front with superglue and make the handle more exaggerated, depending on if you shoot with a full fist grip or with a more straight wrist light grip. either way probably wouldnt hurt,it would just make the bow fit you better. great post though, good luck on finishing your longbow. careful of square corners by the way, the pics didnt show well but make sure youre rounding the edges of the limbs on the front of the bow with sandpaper, then burnishing them with something hard and round. it keeps splinters from lifting and can lead to bad things. keep it up and post if you have any questions, alot of good guys here who are willing to share their knowledge.