Phil, one must do a lot of assuming to use a laser for such POI. Chamber laser? End of barrel laser? Unless it fits the end of barrel perfectly, it's still guesswork because of geometry. The chamber laser, if the barrel is perfectly true and straight, more guesswork.
Pattern your gun/load at 16 to 20 yards as you would sight in a rifle and you'll know exactly where your working pattern center is.
Your dealing with the true pressure line of the shot down the barrel, if it's bent somewhat, all measurements are going to be off. Low to the barrel rib/bead, or one much higher than centerline of bore kinks the numbers also when using geometry alone. There isn't a formula that works for every situation for determining a true POI. The only way to know what it is for you and that gun is to do the work yourself and then you'll know.
Assuming a whole bunch, the 9 inches high at 13 yards will be somewhat close to 27 to 30 inches high at 35 yards.
Phil, if a gun is shooting 9 inchs high at 13 yards that is .692 inches per yard and multiply that by the yardage you are looking for 30 yards=20.76 inches high and 35 yards is 24.23 inches high. So Round if off like V10 said already. Break-em all. Jeff
I would think the shot drop at that distance would be very small. The width of your shot pattern, depending on choke of course, will be around 24" so a half inch of drop (if that much) is not enough to consider.