At the moment there is no firmware update to put the BC aiming point in the PiP window - and personally, I don't think there will be one
However, here is some info I have put together based on actual measurements of the field of view in the PiP box
For the DS35-50 at x2 digital zoom and with the PiP switched on so that there is x4 digital zoom in the PiP window, there is 7.5moa from the centre of the PiP reticle to the bottom of the PiP window
For the DS35-70 at x2 digital zoom and with the PiP switched on so there is x4 digital zoom in the PiP window, there is 5.5moa from the centre of the PiP reticle to the bottom of the PiP window
A couple of examples
1. A 22 rimfire zeroed at 50 yards shooting 40g subsonic bullets with an mv of 1050fps, a ballistic coefficient of 0.12 and a sight height of 2 inches would drop by 5.5moa at 91yards and 7.5moa at 101 yards, so any targets beyond those ranges would have a BC aiming point below the PiP window
2. A 22 sub12ftlb air rifle zeroed at 30 yards shooting 15.89g pellets with an mv of 590fps, a ballistic coefficient of 0.031 and a sight height of 2 inches would drop 5.5moa at 52 yards and 7.5moa at 56 yards, so any targets beyond those ranges would have a BC aiming point below the PiP window
A DS35-70 using x2 digital zoom has a total magnification on the main screen of x14
The main screen DOES show the BC aiming point
If you are shooting at air rifle or rimfire ranges do you really need more than x14 magnification?
Cheers
Bruce