RLH benchmarks all depend on your survey setup: number of questions in each of the ACBC sections (Screeners, Tournament, etc.).
So, I would do two things:
1) Look at your past ACBC surveys that have similar design setup, and calculate the average RLH, and perhaps 10th and 90th percentile RLHs.
2) Use Lighthouse Studios ability (under Test or Field menus) to generate random-responding robotic respondents. Analyze those random responders using ACBC's built-in HB analysis program. Look at the average RLH and perhaps the 90th or 95th percentile RLH from the distribution of random responders.