You may need to reach out to the piping manufacturer for guidance, which they may be prepared to not deliver to you an answer.

If such is the case, it should be on you to "strongly recommend" to not circumvent engineered components as it encumbers your ability to provide realistic results, and that you shall not be held liable for deviations you cannot control.

With that said, if this user has a habit of doing this elsewhere, I would try to compare similar service and material for justification, and make an attempt to match that setup.