DIY Vacuum Forming

This group looks over run with spam, but just in case there are some plastics guys still reading it...
(Posted earlier on another group. Somebody suggested this one.)
I finally decided to make a vacuum formed polystyrene cover for the encoder on the front of the big mill. Seems pretty straight forward. I've got my first vacuum box finished except for the port to put the vacuum hose in. I noticed a lot of the DIY guys make a hole for the smaller vacuum hose even though they have a full size shop vac with the big hose. Is there some reason for that? Seems to me that the larger port for the larger hose would evacuate the box faster and form the plastic quicker before it cools. Am I missing something obvious?
(I have some PETG on the way to play with in case I don't like the way polystyrene forms or holds up)
If this goes well, I have all kinds of ideas for vacuum forming...
(Later after finishing the box and my sheet holder.)
I went ahead and drilled it to fit my big hose for now. If I do much of it I know I'll have to make two or three vacuum boxes anyway. It certainly has plenty of hold for a simple suction test, but not doing any forming. I couldn't lift a board off the box. I was able to lift a sheet of plastic, but only because it would bend. I didn't make it particularly perfect either. I am sure it leaks everywhere. LOL.
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