Dontcha think a 19 tooth sprocket is gonna cut way way down on the initial start from the line?
I have a 790 Speedie and the only reason I dont go to an 18 is that I found that the degradation in first gear pull away is certainly less than with the old stock 16.....a 19 would make the bike seem dead pulling away from a stop light. It'd be outstanding on the slab but ......