Thanks.
Finally issue had nothing to do with DS level.
I discovered my other projects where building correctly so investigated what could be specific to this one.
It turns out that I had by accident in the IMG folder a picture name with accentuated character (like déjàvu.png !).
In that case, the build process works apparently like a charm but generates a 32k file size that of course fails to install.
Sounds like a bug, At least some error message should pop up if supported character set is limited.