following the various suggestions and conversation over the subject, here is the new version of the undertray.
few differences:
1.5 mm thickness intermediate grade aluminium used instead of 2 mm.
no nuts or bolts used, all TIG welded by a professional workshop.
vent in place, partially welded do prevent aluminium distortion.
opening to allow for change of oil and filter without the need to take off the undertray.
pics
as always, feedback and suggestions are welcome.
if any one is interested, pm me. It takes few days to get them done.