Adding missing bones to model

Some w_model used the ValveBiped.Anim_Attachment_LH bone instead of the usual so I tried to decompile the playermodel which doesnt have that bone and add the bones by text to the .qc files, something like below

$attachment "right_hand" ValveBiped.Anim_Attachment_RH 0 0 0 rotate 0 0 0
$attachment "left_hand" ValveBiped.Anim_Attachment_LH 0 0 0 rotate 0 0 0
$definebone "ValveBiped.Anim_Attachment_LH" "ValveBiped.Bip01_L_Hand" 11.472653 -0.000021 -0.000004 0.003842 -6.079197 90.136804 0 0 0 0 0 0
$definebone "ValveBiped.Anim_Attachment_RH" "ValveBiped.Bip01_R_Hand" 11.4749 0.000013 0.000008 -0.362454 -5.599116 -89.631111 0 0 0 0 0 0

It does work but I dont have much experience with modelling so I cant really control where the bone is, which result to the w_model flying above character hands in some cases. Any idea how I can improve it?

blender afaik