@davidhassell as suspected after our discussion earlier, there wasn't anything wrong with the compound querying open/closeed-ness - the tests were failing due to a copy-and-paste error on my part:

diff --git a/cf/test/test_Query.py b/cf/test/test_Query.py
index 553cbace8..3e891aa20 100644
--- a/cf/test/test_Query.py
+++ b/cf/test/test_Query.py
@@ -501,13 +501,13 @@ class QueryTest(unittest.TestCase):
         all_c = [c, c0, c1, c2, c3]
 
         d = cf.wi(6, 8)
-        d0 = cf.wi(2, 4, open_lower=False)  # equivalent to d, to check default
-        d1 = cf.wi(2, 4, open_lower=True)
-        d2 = cf.wi(2, 4, open_upper=True)
-        d3 = cf.wi(2, 4, open_lower=True, open_upper=True)
+        d0 = cf.wi(6, 8, open_lower=False)  # equivalent to d, to check default
+        d1 = cf.wi(6, 8, open_lower=True)
+        d2 = cf.wi(6, 8, open_upper=True)
+        d3 = cf.wi(6, 8, open_lower=True, open_upper=True)

🤦‍♀️ It only took about an hour to work this out 😬 Anyway I have fixed that and all the tests passed. So, now ready for review!

Will add a Changelog entry, also. Commit to follow.

Sorry David I forgot to tag you as requested reviewer last week. All good to review (I resolved one trivial merge conflict in the Changelog for that last merge-based commit).

Thanks David for your useful feedback and offline discussions on this from last week. Updating my local branch now and I'll push everything up when ready for the re-review.

I have just pushed my new commits which I believe address all of your feedback, thanks @davidhassell. All ready to (rock and) roll with a re-review.