You definitely want to use the same imaging equipment you will be using on a regular basis on the mount as you are modelling the characteristics not only of the mount, such as pointing, but more importantly of how your optics and sensors change across the sky as the scope/mount combination moves.
What camera do you have mounted on your 16” RC? Do you know the pixel scale, rough image area and rotation angle? You will need to enter these in the relevant tab for APPM. If your fov is narrow, you may want to use a star catalog with sufficient stars for your plate solves to be accurate enough so that your model is as exact as possible. Also if your sensor is large, you want to bin it at 2x2 at least and perhaps just use 1/2 or 1/4 of its area for the actual images and plate solves so that the whole modelling process doesn’t take too long. APPM will
Try first a small model (20 points or so) just to see everything works. And the acquiring and solving of
Also, as a user of APCC, do you have your meridian AND horizon limits set and enabled? You want to make use of these to do the modelling taking advantage of CW up positions etc. APPM allows for these to be enabled (including safe slews).
In my case, with a permanent setup, I ended doing a 130 point model and was immediately able to image unguided at 1300mm (peanuts for your RC!) getting nice round stars. Both for an 1100 and 1600GTO.