Using Vacuum to hold down sheet metal.

I have some 0.050" thick sheet metal in which I want to drill/mill a
number of holes along with a rectangular cut-out. The G-Code is done.
Things look like they will end up in the right place.

I was thinking of building a vacuum assembly to hold the metal down
while milling. I've put in mechanical stops to prevent shifting but I
was thinking if I built a box and connected the shop vac that I'd be
able to use lots of little 1/8" holes through the MDF frame to suck down
the metal.

A bit of math tells me that the 7 square inches of a 3" diameter vacuum
hose translates into about 575 holes 0.125" in diameter.

But do I really need that many. I plan on only putting holes under the
metal where the mill does not do any cutting so no leaks.

Would this work? Is it better to use a vane type vacuum pump instead?
The milling cycle for all the holes is about 00:05:45 so that would mean
the shop vac would be straining for a fairly long time perhaps
overheating.

Suggestions?

Thanks,

John