I ended up getting an OAG (the Orion Thin Off-Axis Guider), and after the usual frustrations in getting the darned thing focused, I'm having success. No more star marching!
Attached is a single B&W 10 min sub (of NGC 6362 - a somewhat random target that was nearby to my test zone at the time). Round stars! (and no marching across subs). Yes, I know this image is noisy as hell (as I said, only 1 test sub), but it shows that I'm going to achieve what I wanted with the OAG -- long exposures (I kept it to 10 min here due to skyglow + moonlight).
So, I'm happy!
