...I Absolutely Agree! You must keep the Metal Cover in Place, this is part of the 'Firewall'! There has been More than One Incident of the 'Stock' Alternator EXTERNAL Fan/Pulley, Blowing-Up, under High Revs!! The Metal Cover was heavily Dented. Protected Driver!!
To Hold that Cover in Place, I recommend using 'Allen Button-Head' Stainless 'Machine Screws', WITH a 'Flang' built-in. 'Button-Head Flang Screws' (find them on Ebay). These Make it Very Convenient in Removing-Installing these Screws using a 'T' Handle Allen Wrench! Because when installing...you can 'Hang' the screw off the end of the Wrench, slide it in and Rotate Tool, much easier to line-up with Threads in the Nut. The Flang replaces the need for a Washer, that can and will, accidentally drop and be lost in the Abbiss of chassis holes!! Don't use Washers?? It's best to do so, because the Mounting holes are much Larger than the Screw.
...I found that 10-32 NF Machine Screws, can replace the Metric Screws, and work with the 'Captured' Nuts, Perfectly.
With the Factory, Tiny Machine screws with a 'Hex-Head' (No Washer)...I Never liked Reaching-In with a Tiny Socket on a small Ratchet handle or even a Nut-Driver, again No Washer. Some parts would Allways Drop-Off, and could be Lost, Forever!! Be Mindful of the Chassis Holes, Once the Fiber-Glass Cover is Removed. Be reminded, Stainless Steel Screws can NOT be retrieved with a Magnet! You would have to Use a Extended Flex 'Grabber Tool', Inspection Mirror, and a Light Source.
I highly recommend changing over to the 100 AMP Alternator, with the Internal Cooling Fan, and Internal Voltage Regulator. Protected FAN and Get rid of the External 'Junk' Voltage Regulator! IMO
MJ