What miztaj made is more along the size that you would need to grow 1 to 4 plants. You really need the height for a good grow, because if you only make it 4 feet high, you have to account for the reflector and light.
When miztaj finishes his, he'll only have 5.5 feet for a plant or plants to grow(which is plenty and is about half a foot taller than mine), then you have to account for the pot, could be as large as a 5gal bucket, so really when you account for all of that, you'll have about 3.5 feet for the actuall plant...and that's plenty, but even in a cabinet you still have to be selective about what strains you grow, because they will eat up that vertical space very quickly.....I get so tired of people using a fucking rubbermaid box that's less than two feet tall and then posting pictures of their "sick grow".
Miztaj, your cab should be pretty nice when you get everything fitted and Girrah, that's what size you should be aiming for.