I can absolutely attest to this about keeping a bit of older firmwares especially the DSPC firmware part in the processor. We have a forumtopic for this specific firmware part and its influence on soundquality on all DSP modes. It does not affect the upsampling part of the processor so apodizing is unaffected if rolling back to older DSPC. But gain and Trifield width is affected so my favourite atm is the DSPC00044 version where Trifield was never broken and SQ is top notch.

DSPC discussion:
https://www.meridianunplugged.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=156459

I embraced the latest speaker firmware I think all of my speakers worked better together in unity so it stays. The DSP8k speakers felt "taller" initially maybe not so heavy in the bottom. The DSP7200HC got the best result because it sounded not as heavy as before, more slender which works better as it is not sealed as DSP8k. DSP7200HC working better in fullrange alongside DSP8k's with the newest FW.

DSP8000SE, DSP7200SEHC, DSP5200SE sides, DSP7200SE rears, 861v8, 210, Sim2 Ultranero 4, Stewart Cinecurve 2.35:1, XEIT CM-5E Anamorphic lens, Dune HD Duo Cinema 8K and Wireworld Platinum 48G HDMI -> UHD722 -> Shunyata Omega Ethernet. Shunyata/Furutech power-cables/filters. SR Master Fuse@861v8. Uptone Etherregen with 10MHz OCXO clock.