Hi Andy, well I dont have as many options runing on our test 3cx as you do, but I dont seem to remember having to reconfigure anything on 5.1, the only thing that doesnt work is the multiline ring group though you may have seen the postings on the subject they are putting that facility back.
Yes I saw your posting re the GXP2020 and the BLF issue. Not running BLF so not seen he problem though ave upgraded the GXP phones and all seem ok oherwise.
Hope your upgrade goes ok now, and I'll wait for your SHOUT if it doesnt go well.
Regards
Phil