That was going to be my next thing that i said but i have been beaten to the chase!
You have to use a decent guide camera, Load star, SBig402 and the like work well. Qhy5's and what not need a lot of aperture to pick stars up.
There is a reason why i spruke the OAG, because no matter the focal length it is 100% accurate and unless you are a dork and have no idea they are nigh on infallible! the star moves in your oag, it moves in your image plane! the star doesn't move in your OAG it hasn't moved on your imaging circle
Trust me i'm no stranger to flex I have a 1.2m long Newt
with 40cm worth of imaging kit hanging off the OTA.
But yes i see your point that you have gotten acceptable results with a guide scope! aka it can be done