My two cents...
I am of the impression that the frames want to be spun with the top bar out. I believe that I read somewhere that the cells empty more efficiently in that orientation. So while my concept allows either orientation, I have only used it in the above manner. The configuration for spinning deeps required only one additional hole. Drilling a couple of extra holes in the arms was not much trouble and serves to lighten the load. The holes are 1-1/4 diameter which fits Dandant frame tabs nice and tight.
I didn't coat the wood with anything. There are many things that are "aged" in wooden barrels and I doubt that they are coated. The arms are made of poplar which has a close grain as opposed to something like oak which is stronger, but has a very open coarse grain. I think maple would be a good choice too. How many butcher blocks and cutting boards are made from maple and used for food every day? Besides that, the centrifugal force casts the honey to the sides and very little runs down the arms and does not sit there and soak because the honey pools beneath the arms.
The nubs glued along the edges are made from poplar scraps and are to keep the frames aligned in the arms. If I ever remade them, I would use dowels or even nylon cheese head screws. The arms are 1/2 inch thick and have a 1/2 inch block on the bottom with a kerf centered along the shaft center. The shaft has a 1/8 inch roll or spring pin through it for each arm that keeps everything aligned to the shaft, the arms slide over it. The top bar gets a hitch pin through another hole in the shaft over the top to keep everything held in place. The most difficult thing is loading the frames because the darn thing spins so easily. I need to figure out a brake. 8-)
The shaft runs in sealed food grade bearings, but once again there is no contact by the honey anyway. The bottom bearing is mounted in a three inch tall plastic block mounted with 1/4 inch bolts and sealed with aquarium glue (food safe). I calculate it will hold between 3 and 4 gallons of honey, maybe more because the sides of the tub taper outward, before it needs to be drained. I drilled a half inch hole at the bottom and use a cork in it. Low tech and works just fine.
"Your results may vary"
Hope that "chimes" for you. If you want you can PM me and I will send you PDFs with details, geometries and dimensions.