I made inner covers from 3mm ply and ripped some pine to 35x20mm as a surround. Offset the ply in the surround so I have 5mm one side and 12mm the other, this let me cut a 10mm deep notch in the 12mm side that I can use as a top entrance depending on which way up the cover is placed. Drilled a hole in the centre with the biggest hole saw I had and I can place a jar feeder over it or leave it open and sit a couple of inverted jars on smalls bits of timber sitting on the inner cover. My jar feeders are the biggest jars I could find (1-1.5L) with 1.5mm holes drilled in the lids.
Winter has hit here the last few days, dropped below freezing Wednesday night for the first time, we have had frosts every night since. Day temps are still making mid to high teens c, all my hives were flying early yesterday afternoon and I could see pollen coming in.