I've been trying to create a travelling astro imaging setup using a Star Adventurer and an Altair 70ED refractor (not the APO unfortunately). I've not been having much luck with it until now, but after getting a QHY Mini Guide scope and camera to add to the setup things have improved considerably. I'm not sure if it's the better polar alignment I get by using the guide camera and sharp cap pro, or if it's the guiding, but I've been able to do pretty reasonable 10 minute exposures with a 420mm scope on a cropped frame Nikon D7500, so around 630mm equivalent.
This is my first successful image at deep sky imaging and is a combination of 30 x 60s, 10 x 90s, 10 x 120s, 5 x 240s and 2 x 600s @IS0 1600. I wish I'd done more longer exposures, but I didn't entirely trust the mount. The graph in PHD2 showed a lot of work being done to keep things on track.
But you can definitely mount a 70mm scope and DSLR on a Star Adventurer and get usable images from it. I've not modified or tuned the mount in any way, but I have added an additional counterweight to make the payload balance.