I use my 1992 vintage A-P portable 8-inch pier with my 1100GTO mount. It is rock solid, even with a 180 EDT scope, 16 megapixel camera, and piggybacked guide scope attached. I set up and take down my gear including the pier every time I get it out.
I didn't anchor my pier in concrete, but I did pour 8-inch diameter concrete pads about 2 ft deep into the ground to give the pier legs a solid base to sit on. if I had a permanent observatory I would try to figure out a way to lock the legs into position so as not to disturb the polar alignment.
The biggest challenge I had with my old A-P pier was getting the 1100 mount base firmly attached to it. The top of the original pier was not perfectly flat, so I had to hand scrape the high spots so that the mount base made even contact with the top of the pier. The old piers only have three holes for attaching the mount base. I drilled three additional holes in it so that I could attach the mount to the pier using all six screws. Finally, I use NORD-LOCK lock washers on the screws that attach the mount base to the pier to prevent the base from shifting in the pier when everything is attached.
I hope this information is useful.