BN15 Custom Calculation for a 401k Plan

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Is anyone using a Contribution Type of (X) for Custom Calculation on their 401k plan to limit the company match for employees over the age of 50 to their first $17,500 of contributions? Is it possible to have a match limit of $17,500 but allow the associate to have a contribution limit of $23,000 within one plan and not use a Custom Calculation?

We currently have our catch up deduction defined as a separate deduction with a $5,500 limit and use a BSI group code to allow associates over the age of 50 to exceed the $17,500 limit. We would like to do away with the separate deduction and have one benefit plan that allows the associates to exceed the $17,500 limit for contributions but not match any contributions above the $17,500. Is anyone currently doing this?