My guess is that this is a small company and the participation is carved out to cover only the highly-compensated employees. They have to hire an actuary to install a DB plan and he planned it, probably very carefully to exclude the 5 persons not in pay status. So I am not optimistic for you.
If you want to pursue it, you can file a complaint with the US Employee Benefits Administration. To learn how to file a complaint go to the below website. Its 4th paragraph covers that.
DISCLAIMERâ€”This answer is for informational purposes only under the AVVO system, its terms and conditions. It is not intended as specific legal advice regarding your question. The answer could be different if all the facts were known. This answer does not establish an attorney client relationship. I am admitted only in California. (Bryant) Keith Martin sbbizlaw.com