I have always built skinny/micro shaker doors in the shop with veneer or mdf 3/4" panel and 15/16" x 15/16" hardwood frame edge glued up flush to the back of the panel. However the added work pushes past some budgets. I can purchase a routed mdf door from 3/4" material. My worry is that removing lets say 3/16" of material from 90% or more of one side of mdf is going to cause flatness issues (and also paint? How to deal with the fuzziness of routed mdf). Anyone doing this and what are your results? I guess a routed normal shaker door would be a good enough equivalent to judge by and I know guys are doing it. It just makes me uneasy dropping off $60k in cabinets without experience in this area. Would love to hear some feedback before I sell this to anyone. Thanks, Robert

We do routed MDF doors. They Bow terribly sometimes, the larger the door the more issues. It seems to be worse sometimes than others depending the latest batch of MDF. I don't do skinny "sitles/rails" but I would say you are right that will only make the bowing worse.
Painting isn't a problem as long as you are useing good MDF (double refined), just sand with fine grit and it will finish nice.

We started routing a .040 deep outline of the "panel" with a v groove bit on the back side of the door to help balance it. Made a big difference. Very little warping.

Gary do you think this is as effective as routing an entire relief on the back side? that is what I have been doing, but if an outline with a v bit does the trick that would save lots of time

We haven't tried that. Honestly, we have made many doors with no machining on the back side and have had very few problems. The biggest help is with the v groove on back, which is machined first, is that the final squaring of the corners is even with the rest or the machined panel on shaker doors. That final pass done with an 1/8" diam. bit was many times a few thousands too deep or not quite deep enough because the mdf would move slightly as the panel area was machined. This added to sanding time. We do notice less warping of the doors also. It is, of course, also faster than machining the entire panel on the back side.

We had the same problem with warping so much so we tried leaving a 2" space around each door. Our fix was to use a 5/8 mdf panel and rout the ring on the cnc out of 1/4 material. Then run through the wide belt to remove the unwanted material leaving only the ring at 1/8 and then just glued and pin nail the ring onto the 5/8 material so the door finishes at 3/4 thickness. Very little sanding this way