The Decree of 10 Thermidor AN XII (29 July 1804) directed that the organization of the Grenadiers a Pied and the Chasseurs a Pied was to be of two battalions per regiment, each of eight companies. Each regiment also had a battalion of velites organized in five companies.
The Decree of 15 April 1806 directed that each 'corps' (Grenadiers and Chasseurs) be reorganixed into two regiments each, each regiment comprising two battalions of four companies each. There was now to be a regiment of velites in each corps, of two battalions each.
The Decree of 1 October 1808 directed that the Grenadiers and Chasseurs be reorganized into one regiment each, of two battalions each. Each regiment would now be composed of eight companies.
On 19 September 1806, the velites became the two regiments of Guard Fusiliers (Fusiliers-Grenadiers and Fusiliers-Chasseurs.
This information is contained in La Garde Imperiale by L. Fallou.
The Decree of 16 January 1809 reorganized all of the Guard infantry regiments then in existence (Grenadiers, Chasseurs, Fusiliers-Grenadiers, Fusiliers-Chasseurs, Tirailleurs-Grenadiers, and Tirailleurs-Chasseurs) to be organized in two battalions of four companies each.
This decree is contained in Volume 1 of Saski's Campagne de 1809 on page 506.
Company strength would vary under each reorganization from 80 plus NCOs, officers, and musicians in 1804, to 120 plus in 1806, to 200 in 1809.
Is there a decree or evidence of a battalion of six companies that I have missed?