Just to add up on my problem, I'll describe what I did to get the boot disk:
First I tried what I usually do (at least with my Lenovo x220 works ok):Installed the "Sierra installer" to the pendrive using the createinstallmedia tool
Using clover mounted the EFI partition from the USB drive
Extracted the EFI folder from the FrostyTheSnowman bootpack and copied it to the EFI partition
Overwrote the ACPI folder and config.plist with the version attached by Jake Lo to the post (i7-3740QM.zip) and modified the config.plist file to correct the SSDT-aml error.
Connected the USB pendrive to the laptop, setup the bios as per the instructions: AHCI enabled, secure boot disabled, Optimus enabled
Booted to clover, selected the usb entry and was greeted with a black screen.
Then, I opted to follow Jake Lo's procedure and created the USB installer following his guide, but using the bootpack from this post as described above.
Did I miss something?