diff --git a/howto/new-machine-cymru.md b/howto/new-machine-cymru.md
index eb0b9aea8f2a7f61d3105264dbeb0961bc3c4953..12ef9990a136dd845180ed632a371ac89b770961 100644
--- a/howto/new-machine-cymru.md
+++ b/howto/new-machine-cymru.md
@@ -214,6 +214,12 @@ See [howto/new-machine](howto/new-machine) for post-install configuration steps,
 
 IMPORTANT: Do not forget the extra configuration steps, below.
 
+Note that it might be possible to run this installer over an existing,
+on-disk install. But in my last attempts, it failed during
+`setup-storage` while attempting to wipe the filesystems. Maybe a
+`pivot_root` and unmounting everything would fix this, but at that
+point it becomes a bit too complicated.
+
 ### boot setup
 
 TODO: in the last attempt at following this config ([ticket