How tall was my 3x-great-grandfather Denis Killeen (1786-1850)?
According to his record of service, he was 5 foot 8 when he enlisted in the 97th Regiment of Foot at the age of 18, in 1804; and six years later, at the age of 24, he was 5 foot 10:
This from a newly added database at ancestry.ca: Canada, British Regimental Registers of Service, 1756-1900.
Note: Ancestry.ca has recently added a number of new databases. Worth checking out.