How can I boost the field length norm in elasticsearch function score?

Question

I know that elasticsearch takes in account the length of a field when computing the score of the documents retrieved by a query. The shorter the field, the higher the weight

Answer 1

I have something that kind of works. With the following, I deduct the length of a field of my interest from the score.

{
 "query": {
   "function_score": {
     "boost_mode": "replace",
     "query": {...},
     "script_score": {
         "script": "_score  - doc[''].value.length()"
     }
   }
 }
}

Hovever, I cannot control the relative weight of this number I am subtracting, compared to the old score. That's why I am not accepting my answer: I'll wait for better ones for a while. Ideally, I'd love to have a way to access the field length norm function within the script_score, or to get an equivalent result.