performance shortboard

i have a young kid who wants me to make him a board. this kid rips and thinks his current board is holding him back. current board dimensions are 19.5 wide 6’2 long, 2 3/8 thick squash tail. He was thinking about going down to 6’ and 18.5 wide 2 2/8 rounded pintail or would does anybody have any suggestions on board dimensions and tail shapes that would pick up his surfing he wants to go more vertical but gain speed. thanks