Queen cells have gone out

I aim to replace most of our queens this time of year using the supercedure impulse. At this time of year many colonies will replace an older or poor performing queen by raising a single cell, allowing it to hatch and mate resulting in a young healthy queen to go through the winter.
The method I use tries to replicate this by placing a sealed and protected queen cell in each hive which will hopefully be accepted by the colony as their own. The virgin then emerges from the cell, mates and I have young queens going into winter.
This system has a fail-safe in that if the virgin fails to emerge and mate we still have a viable queen established in the hive.
Not the situation when replacing existing queens with new mated queens as the resident queen has to be removed or destroyed before her replacement can be introduced. So any acceptance problems of introduced mated queens will result in a queenless colony.
The bar of cell cups before grafting, six days before they are installed in the colonies.
Each cell is wrapped in tin foil to prevent the colony ripping out the side of then cell and destroying the larvae. We have used electricians insulation tape but stopped when a local bee keeper lost three batches of sixty cells due to some fire retardant on foam he was using. I suspect that electricians tape will have some fire retardant so decided not to take the risk.
When installing the cells I open all the hives on the pallet, fill the feeder then prise apart two frames in the centre of the brood nest and push the cell in, put the lid back and jobs a good'un.

The success rate of this method will vary according to the weather but I estimate it to be between 50% and 75% of cells introduced becoming mated queens.
Will check again in three weeks and any colonies without a laying queen will be united for the winter.