hello. I'm trying to do some poly modeling for a pickup truck. I want to put in some vents on the hood and I'm having problems. The idea is to model in poly and then "convert smoothmesh preview to polygons." I'm trying to subdivide a face and then extrude the subdivisions down to create the slots of the vents, but i can't keep the corners of the face square. It doesn't matter how many edge loops i put in, whenver i hit 3, the corners collapse. So instead of getting linear slots, i get curved slots. I assume i must be going about this wrong. Do i have to put in edgeloops for the entire truck body to get these vents? that seems like it would add a lot of complexity where i don't really need nor want it.
thanks guys

reference image:


poly model:


poly model with smoothing (3 key):

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