As the question says; do I have any options of setting/defining my own Search- and Request-Handlers for Sitecore ContentSearch, based on the active site?

Skimming through ContentSearch configs, I'm not even sure where the default SearchHandler is defined, much less if there is code anywhere than I can hook into, to control it.

As the question says; do I have any options of setting/defining my own Search- and Request-Handlers for Sitecore ContentSearch, based on the active site?

Skimming through ContentSearch configs, I'm not even sure where the default SearchHandler is defined, much less if there is code anywhere than I can hook into, to control it.

Example:

Scenario could be; where we have say /products and /productsinstock search handlers; where the latter one would - as an example - the following filter added.

<lst name="appends">
  <str name="fq">inStock:true</str>
</lst>