Yes, you are right about 4.11 and UP3 not being compatible at press time. I did this as the very first thing, installed 4.11 over my existing UP3RC4 install. It loaded the main screen (with stock selected in the JSGME) but when I clicked QB it all froze. This is happening now with my vanilla install as well, so it might not have been a compatibility issue, but a 4.11 issue.
In any case, I would advise a fresh vanilla IL2 install if you want to take advantage of the quantum leap in capability that 4.11 provides. I like the mod packs for more planes that I never fly, but the new AI in 4.11 makes not having my B-25 strafer something I can live with.
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