You should first check your math. Going from f:16 to f:469 is 9.75 stops. That's a lot more than a 7x increase in the number of flashes needed. To gain 1 stop it's 2X the number of flashes, 2 stops is 4X the number of flashes. The factor is 2 raised to the power of the number of stops, so three stops is 2^3, or a factor of 16. 9.75 stops requires multiplying the amount of light by 860. By that time you're going to be seriously off due to the nature of adding sequential shorter exposures, and perhaps a bit bored and off on your count.