For shoulder width look for "rightArm.ty":and "leftArm.ty" - Change both to same number
*****Make sure there's always a (,) after your number Example (15.0,)******
For arm length look for "rightHand.ty": and "leftHand.ty" - Change both to same number
For short arms use (26.0,) and for very long arms (29.0,) but you can adjust to your liking
For body length look for "spine2.ty":
Increasing the number shortens the torso and lengthens the leg appearance. Decreasing the number lengthens the torso and shortens the leg appearance

For neck length look for "head.ty":
Increasing or decreasing the values will change the neck length
How accessories fit is controlled by below items:
"forearmTHIN": 0, self explanatory (If too loose increase value/If it clips decrease value)
"forearmTHICK": 0, self explanatory (If too loose decrease value/If it clips increase value)
"upperarmTHIN": 0, self explanatory (If too loose increase value/If it clips decrease value)
"upperarmTHICK": 0, self explanatory (If too loose decrease value/If it clips increase value)
"trapTHIN": 0, self explanatory
"trapTHICK": 0, self explanatory
"neckTHIN": 0, ?
"neckTHICK": 0, ?
"chestTHIN": 0, how tight or loose jersey fits around upper chest area (If too loose increase value/If it clips decrease value)
"chestTHICK": 0, how tight or loose jersey fits around upper chest area (If too loose decrease value/If it clips increase value)
"breastTHIN": 0, unused (for female png's I assume)
"breastTHICK": 0, unused (for female png's I assume)
"absTHIN": 0, how tight or how loose jersey around waist area
"absTHICK": 0, how tight or how loose jersey around waist area
"headTHIN": 0, ?
"headTHICK": 0, ?
"shoulderTHIN": 0, how tight or how loose jersey around outter shoulder area (If too loose increase value/If it clips decrease value)
"shoulderTHICK": 0, how tight or how loose jersey around outter shoulder area (If too loose decrease value/If it clips increase value)
"hipsTHIN": 0, how tight or how loose shorts fit around waist area
"hipsTHICK": 0, how tight or how loose shorts fit around waist area
"thighTHIN": 0, how tight or how loose shorts fit around thigh area (If too loose increase value/If it clips decrease value)
"thighTHICK": 0, how tight or how loose shorts fit around thigh area (If too loose decrease value/If it clips increase value)
"calfTHIN": 0, how tight or how loose socks/leg accessories fit (If too loose increase value/If it clips decrease value)
"calfTHICK": 0, how tight or how loose socks/leg accessories fit (If too loose decrease value/If it clips increase value)
The best way to judge how the accessories should fit is to find a player model of similiar size and copy the values and play around with them until you
get the results you like.