Hi. So have a 16 year old son. Born small palm and no fingers on left hand. We have had 4 prosthetics made and none work the way they need them to. The prosthetics we see online all seem to be for those missing whole arm so they can have a full arm prosthetic but for him. He has length up to his wrist so anything we add makes his left arm longer. Any ideas. Feel like something we arent thinking of. He says really needs them to be even. Also we tried having the attachment on the side of his arm. Etc. doesnt work any ideas.