CREATE TABLE table_name_27 (year_of_most_recent_appearance INTEGER, year_of_first_appearance VARCHAR(255), corps_name VARCHAR(255))
What is the average year of the most recent appearance of the Boston Crusaders, who had their first appearance after 1976?
    
SQL: SELECT AVG(year_of_most_recent_appearance) FROM table_name_27 WHERE year_of_first_appearance > 1976 AND corps_name = "boston crusaders"