Hi. Seems like setting the weights via code is the only option if you are not using UnifiedSearch. That seems weird that the admin ui weights only work with UnifiedSearch. It would be very un-intuative, for instance, if you had different searchs that used both UnifiedSearch and .Search, and weights in the admin worked for one and not the other. Seems like it should work for both. 

You should be able to fetch the weights set in the UI 

var unifiedWeightsQuery = 
SearchClient.Instance.NewCommand(context => new UnifiedWeightsCommand(context, SearchClient.Instance.DefaultIndex));

UnifiedWeightsItem weights = unifiedWeightsQuery.Execute().Hits.FirstOrDefault();

and apply them when specifying .InField(fieldName, relativeImportance)

Usually, there is a sorting option that the user can use (Relevance, Date Asc/Desc). If one is set, the search result won't change because an orderBy has been applied and the result is no longer sorted by score. What we had to do was to end the query with the following extension

.ThenByScore() (Credit Henrik Lindström) https://gist.github.com/lindstromhenrik/9779858

To make sure that the score is actually taken into account after the inital sorting has been applied.

Then we created a custom "Boosting Settings" page type, where the editor can set the boosting multiplier for custom properties, and included that in the search query as well as ITypedSeach extension, something like

.AddCustomBoosting(searchRequest)

Then the function

public static ITypeSearch<T> AddCustomBoosting<T>(this ITypeSearch<T> query, SearchRequest searchRequest)
	where T : CustomPageType
{
  if (!string.IsNullOrEmpty(searchRequest.Query))
  {
    var queries = searchRequest.Query.Split(' ');
    foreach (var word in queries)
    {
      var cleanedWord = QueryEscaping.Quote(word);
      query = query
      .BoostMatching(x => x.DisplayName.AnyWordBeginsWith(cleanedWord), _siteSettingsPage.Content.BoostDisplayName)
      .BoostMatching(x => x.PageTitle.AnyWordBeginsWith(cleanedWord), _siteSettingsPage.Content.BoostPageTitle)
    }
  }
  return query;
}

Does this make sense?

Thanks all of you! Hopefully I can make something out of this :-)