Attempting to retrieve nested data for a relationship

Forum_PostService.php

Note: replies.user is throwing a mysql error. Basically, want to be able to retrieve a Thread with all Replies, then each Reply has a user object

{{ thread.user.fullName }} works fine, but not {{ thread.replies[0].user.fullName

<?php
// Forum_ThreadService.php
if ($record = $this->threadRecord->with(['user', 'category', 'replies', 'replies.user'])->findByPk($id)) {
  return Forum_PostModel::populateModel($record);
}


// Forum_ThreadRecord.php
public function defineRelations()
{
  return [
    'category' => [static::BELONGS_TO, 'Forum_CategoryRecord', 'categoryId'],
    'replies'  => [static::HAS_MANY, 'Forum_ThreadRecord', 'parentId'],
    'user'     => [static::HAS_ONE, 'UserRecord', 'id'],
  ];
}

// Forum_CategoryRecord.php
public function defineRelations()
{
  return [
    'threads' => [static::HAS_MANY, 'Forum_ThreadRecord', 'categoryId'],
  ];
}

ForumVariable.php

<?php
namespace Craft;

class ForumVariable
{
    public function getThreadById($id)
    {
        $record = craft()->forum_thread->getThreadById($id);

        // This gets me the nested relationship data I am wanting (user.email, user.fullName, etc)
        $record->replies = array_map(function($reply)
        {
            $reply->user = UserRecord::model()->findById($reply->userId);

            return $reply;
        }, $record->replies);

        return $record;
    }
}