From my experience, the best way to solidly mount a dial with no feet on an Eta 28xx is to use a spacer that: 1 - fits around the movement with little or no side to side movement 2 - fits snugly inside the inner diameter of the case with little or no slop 3 - can be used with case clamps and screws 4 - rises above the top of the movement and eliminates the original el cheapo thin, flexy calendar spacer. The dial can be held in place by 'dial dots' during assembly and the case clamps/screws will hold it all firmly in place.
Where to find such a spacer? The CNC made 'Stilty Spacer' was the best but Stilty has gone south (or north). This leaves other custom made spacers and Yuki has them but they are pricey. For a first class project there are few $hortcut$ though.
Here are the dimensions of a rolex 16220, 1016, 5512/13 spec case to Eta 2836/46 Stilty Spacer: OD = 28.5mm with a step down to 27.45mm about half way down the outside edge on the dial side. ID = 25.6mm with a step out to 26.0mm on the dial side about half way down the inside wall. Thick = 2.2mm. A spacer like this will allow an Eta 2846 with no date works or spacer to be mounted in a 5512/13 or 1016 spec case with the correct dial. Remember that MBK cases are basically rolex 1680 spec inside but most will have 5513 size 26.0mm dial openings no matter what reference number so spacers etc will be different sizes.
The Stilty Spacer specs above are from the spacer I used in a '1016' project with a genuine 16220 case, Eta 2846, and genuine spec dial with feet removed. No flimsy oem Eta calendar spacer was used. The 16220 case inside dimensions are about the same as the inside of a genuine rolex 5512/13.
Before I put the Eta 2846 in the 16220 case in 2008, I put a rolex no date 1570 (without any calendar parts or spacer and with low profile no date center wheel/cp, hour wheel etc) in a 16220 with a genuine 1016 dial in 1997 and it all went together with no hassle at all. This was before RWG, Stilty Spacers etc and the watch that the movement came in only cost $450 back then...a rolex 1505 opd with tt bracelet.
Stilty Spacer https://rwg.cc/topic/116411-yuki-eta-2824-adaptor https://rwg.cc/topic/74384-noobmarniner-movement#comment-453732
Yuki spacer info https://yukiwatch.ecwid.com/#!/ETA-adaptor-set/c/6702300