Maybe this info will help:

Cabbages thrive when planted with herbs such as dill, mints, rosemary, thyme, and chamomile. Cabbage also grow well with other vegetables and are good companions to onions, garlic, peas, celery, potatoes, broad beans, and beets.

PROPAGATION / SOWING OF CABBAGE:
Plant cabbage seeds 1/4 to 1/2" deep. Transplant or thin small cabbage plants to 15-18" apart in rows 32-36" apart. Cabbage Transplants can be started in April for May planting. Transplant after 4-6 weeks. Use a starter fertilizer, soaking the root ball thoroughly prior to transplanting. Direct seed in late spring, as seedlings can tolerate a light frost. Cabbage can be direct seeded up until mid-late June for a continuous harvest. Ideal soil temperature for cabbage should be 21-26°C (70-80°F) for optimal germination in 4-7 days.

CARE & GROWING OF CABBAGE:
Cabbage prefers full sun, but will tolerate part shade. Prepare a rich, loose soil that holds moisture well and has a pH level of 6.0-6.5. Cabbage is a heavy feeder and will also benefit from applications of boron, calcium and magnesium, particularly during the early stages of growth. To help deter Cabbage worms, use row covers in the earlier part of the growing season - this will prevent moths from laying eggs on the plant. It also helps to manually remove cabbage worms if visible

So to answer the question...you could use a light shade (40-50%) but it will probably be fine as long as you keep it watered.

Miwa

Here is a link that might be useful: Shade Cloth

I really don't have a lot of advice for you other than to tell you good luck. I've tried to grow cabbage two years in a row with no success. Last year I planted four cabbage as seedlings and they bolted. This year I planted the seeds directly in the ground and still my cabbage bolted.

I had a fair amount of sun (6 to 7 hours), fertilizer, and a shade cover for the really hot weather (85 and above). I am not sure I want to bother with cabbage any more. It's isn't my favorite veggie so no loss.