Patching Dell Custom ESXi 5.5u1 Image with VMWare Patch via esxcli software vib Commands

Hello,

I have a PER820 running a custom ESXi 5.5u1 build 1746018 (taken from R820 driver download page). It is connected to EqualLogic storage and has MPIO drivers installed. I want to apply these VMWare patches (52406) to deal with Spectre and Meltdown via esxcli software vib commands.

Is it safe to do so? Or is there a custom image with these patches installed in them? I noticed that there are ESXi 5.5u2 and 5.5u3 images in the driver download site. Do I have to update ESXi first to the latest available version to be able to apply the VMWare patches (via esxcli software vib commands)?