So, i was able to find today's password and log in.
It seemed that volume was indeed found without a problem.
I deleted my P410 raid configuration, instead of creating 1 logical volume of my 4 disks, i created 4 volumes with 1 disk each.
Synology web assistant was able to install the .pat file and reboot. Reboot gave a lost config status.
Then i tried with the Synology assistant application, same result.
I don't know where to search for informations.
(During Raid creation i can see errors telling synoacl has not been loaded, unable to mount with synoacl... and some message like synoacl_vfs synoacl_ext4 not loaded)
I just gave a try with the latest beta from Trantor using the SAS/HBA .img everything looks to be working like a charm !