By 1809, I think all ranks except drummers wore the knapsack in the conventional way (ie slung from the shoulders); the exception was supposedly to allow the drummer to sling his drum over his shoulder on the march.
Just out of interest, what would have determined which of the German regiments were wearing the shako in 1809 (if any). Would it have been prestige/seniority - eg IR No.1 (or possibly IR No.4 who were all Masons - or so I've read)? Or the geographical location of their depot/inspection area?