diff --git a/prototype/tango-prototype/README.md b/prototype/tango-prototype/README.md
index eb7ef1a..15b0d21 100644
--- a/prototype/tango-prototype/README.md
+++ b/prototype/tango-prototype/README.md
@@ -4,15 +4,30 @@ Tango prototype TODO list
 
 __ The current checkpoint implementation is fundamentally broken and
    needs a rewrite, or else.
+   This issue is not mentioned at all in the Tango paper.
+
    option 1: fix checkpoint to be 100% correct
    option 2: checkpointing is for the weak and the memory-constrained, so
              don't bother.  Instead, rip out the current checkpoint code,
              period. 
+   option 3: other
 
-__ Checkpoint fix option #1: history splicing within the same OID?
+xx Checkpoint fix option #1: history splicing within the same OID?
 
-__ Checkpoint fix option #2: checkpoint to a new OID, history writes to both
+xx Checkpoint fix option #2: checkpoint to a new OID, history writes to both
                              OIDs during the CP, then a marker in the old OID
                              to switch over to the new OID?
 
+History splicing has a flaw that I belive just won't work.  The switch to a
+new OID has problems with updates written to the old OID before and before the
+new checkpoint has finished.
 
+I believe that a checkpoint where:
+    * all Tango writes, checkpoint and non-checkpoint alike, are noted with
+      a checkpoint number.
+    * that checkpoint number is strictly increasing
+    * a new checkpoint has a new checkpoint number
+    * scans ignore blocks with checkpoint numbers larger than the current
+      active checkpoint #, until the checkpoint is complete.
+
+... ought to work correctly.