Which Meade SCT? I assume an 8"????
Over the years I've used all the different Meade SCT's.
The Meade focuser is completely different to the one used on the Celestron.
It's not as repeatable or as rigid.
Mirror slop/ flop can be reduced by running the mirror up and down the baffle tube - turn the focuser about 30 times in each direction. This re-spreads the grease on the baffle and reduces the gap and hence the slop.
It is possible to make and fit a mirror lock which can then be used to hold the mirror in the final position. Not 110% but can work well.
(Google Meade Classic LX200 mirror lock)
https://www.youtube.com/watch?v=6CIe0YsQbI8