Well gents, after months of head scratching, software fiddling, driver updating, setting changes, etc, I think I've finally cracked it with my CTD and BSOD issue.
Thanks to everyone for chipping in over the past few months with ideas, threads, articles, moral support and welcome ridicule as I've got more and more fudged off.
Last Thursday, prompted by Kev's suggestion (cheers!), I ran the rig with the new pair of RAM sticks removed, leaving the original older pair. For those online at the time, you recall it was the first time since the upgrades I had a evening without DCS crash or BSOD.
Today, after some testing, it appears that just by switching the locations of the old and new modules, I can run the full 64GB and the crashes are gone. CPUZ shows timings all match and I ran some RAM stress tests without a single error.
After putting DCS through its paces in VR, both online and offline, all seems to be well and the smoothest it has been.
More importantly, the weird resolution noise / deterioration I've experienced in VR since the upgrade has completely disappeared and I've reset the slices registry entry back to default.
Finally, hopefully, I can enjoy my Thursdays again