The enderman scale is not tied to random entitys.

Its the custom model which changes the scale using the mob id as seed

if you open the enderman file in the cem folder there will be some lines

"body.sx": "random(id)/3+0.83333333334",
"body.sy": "random(id)/3+0.83333333334",
"body.sz": "random(id)/3+0.83333333334",

Yo need to change "random(id)" to something that fits you. In your case as the orignal is a ranodm between 0 and 1:
"1"  (body.sx": "1/3+0.83333333334",)

Above is a line that puts the enderman back on the floor:
"body.ty": "if(is_on_ground,abs(sin(limb_swing/4))*2*limb_speed,0)-14.75-sin(age/8+1)/4-(random(id)-0.5)*13",



Again change random(id) to your desired point (1).

That should be all