I have a new 99 with adjustable comb. I took it to the range to do some pattern work a week ago. I did not move the comb from the factory setting. Using STS Nitro's 1 1/8 of 7 1/2 shot and a Light Modified extended choke at 16 yds. with a figure eight sight picture came out about 60/40. I fired three rounds standing at the same pattern board to get a good average. When I switched to a full choke at the same distance, the wads were going through about 4" above the '+". and the shot density held true as the LM choke.
Same here for a 2 yr old BT-99 Grade III. 60/40. But they made different guns with different POI. They say you can find out the intended POI on BT's by the serial number. Maybe you can check with the company. I've found them good about queries like that.