I have a 14.5" corrected Dall-Kirkham (f.l. 2470 mm) on a non-AE 1100 in a permanent observatory. Typical setup is an image scale of 0.4 "/pxl!
With a 200 or more point APPM model, I can go unguided for up to 15 minutes at times. It is likely related to the Dec of the target, but I can't quantify that theory. I have not tried Dec arc modelling yet.
Attached is a comparison of three images with the above setup. "Corrected tracking" = using the APPM derived model.
My conclusion is that, while unguided at this focal length is achievable, the real goal is good images. Hence, I tinker with unguided, but I usually guide. OAG and PHD2.
With a 910 mm focal length refractor (image scale 1.5), I image unguided all the time. PHD2 is fine when needed, but it adds a layer of potential 'disruption.' Its all a tradeoff!