PEO plan for NHCE, not for HCE/Owners

Does anyone have any good resources, articles, webinars, links  etc on how testing is impacted when rank and file workers are handled through a PEO as their employer, but the owners are not? 
I've done some searches here on BenefitsLink but haven't some across anything particularly useful, but please feel free to share links to other related threads too. 

The PEO workers are covered by the plan offered by the PEO, the owners are not, and want the business to sponsor its own plan. 

I am fully aware PEO co-employment is NOT the same as Leased EE status, which is why I'm asking. I've had some sponsors argue that the NHCE are not their employees at all, which doesn't seem right to me, but I am not well versed in PEOs, and I'm sure there are varying flavors, so who knows. 

Think basic 401(k) plan with a safe harbor provision. 
Thanks folks!

Your best bet is the ERISA Outline Book.  Start with an advanced search for "peo" and "hce".

You should review the agreement between the PEO and the company, the PEO plan, and the proposed plan for the company.  You also should look at the PEOs payroll practices, vacation, holidays, work schedules and other similar time for which employees receive compensation.  It is fairly easy for an arrangement with a PEO to be treated as a leasing arrangement due to how the PEO functions operationally.  Do not rely solely on representations about the status of the employees from the PEO or from the company.  Facts matter more than representations.

It is very likely that the PEO employees working for the company will need to be considered in coverage and nondiscrimination testing for the company plan.

Thanks Paul, I'll start there. 

and yes, copies of the agreements and documents have been requested. These seem to be more and more common, so I need to get more familiar with the impacts.