You are working way to hard, and just asking for trouble.
Pick a safe amount close to the 415 limit and use the maximum funding limit to keep the plan overfunded. Then, in the 9th year, or when he starts wanting to terminate, calculate the maximum benefit and make sure the assets don't exceed that amount.
This works great, especially if you don't have any other participants.
IMHO, the 415 limit is too fluid to try to match every year.