This is where you can and SHOULD change the scale:
;---face draw info ; Šç•`‰æî•ñ
;; fv30-36
;; player-main: f20-21: pos_x/y, f22-23:scale, f24-25:alpha, f26:spr-priority
;; player-partners: f30-31: pos_x/y, f32-33:scale, f34-35:alpha, f36:spr-priority
;sys::lifebar_face_partner_info ; ƒp[ƒgƒi[Šç•`‰æî•ñ
;;--- player-main
trigger1=1|| fvar(20):=var(31)/fvar(0) + (var(30)+42.5) *ifelse(teamside=1,-1,1) ;;Pos_X [142]
trigger1=1|| fvar(22):=var(32)/fvar(0) - 3 ;;Pos_Y
trigger1=1|| fvar(24):=0.11 || fvar(26):=0.11 ;;Sacle_X/Y
trigger1=1|| fvar(28):=256000 ;;Alpha_SSS/DDD
trigger1=1|| fvar(32):=var(46)+1 ;;Spr-Priority
;;--- partners
trigger1=1|| fvar(21):=var(31)/fvar(0) + (var(30)+42) *ifelse(teamside=1,-1,1) ;;Pos_X [136]
trigger1=1|| fvar(23):=var(32)/fvar(0) + 18 ;;Pos_Y
trigger1=1|| fvar(25):=0.082 || fvar(27):=0.082 ;;Sacle_X/Y
trigger1=1|| fvar(29):=256000 ;;Alpha_SSS/DDD
trigger1=1|| fvar(33):=var(46)+5 ;;Spr-Priority
;---
trigger1=1|| fvar(34):=ifelse(teamside=1,-8,8.5) || fvar(35):=8.9 ;;OffSet_X/Y
trigger1=1|| fvar(36):=0 ;;OffSet_Scale_X&Y
In fvar(24) you can change the X scale of your character Portrait and in fvar(26) the Y scale
trigger1=1|| fvar(24):=0.11 || fvar(26):=0.11 ;;Sacle_X/Y
In fvar(25) you can change the X scale of your PARTNER Portrait and in fvar(27) the Y scale
trigger1=1|| fvar(25):=0.082 || fvar(27):=0.082 ;;Sacle_X/Y
Just change that values.
EDIT: you have to understand that changing this values will be change ALL the portraits scales. The other way is changing the values inside the explod like Mark said to you.