How Many Plants

[FilthyRich]

Hi everyone; first post for me. Greetings!
I have a raised garden bed 3m (10ft) x 1.2m (4ft) where I will be planting a number of tomato seedlings that I have raised myself. I recently saw a TV program that showed a grower who used a method where a number of plants were each grown on a single cordon up a wire to a horizontal lattice. Once the plants reached the lattice they were allowed to develop side shoots which eventually covered the lattice, shading the garden bed below, and causing the fruiting trusses to hang like grapes below the canopy above.
I hope to give this method a try and am wondering if anyone else has had experience with this or a similar method.
I would be particularly interested in your view on how many plants you think my 3.6 sq m (40 sq ft) plot could support and how high you think the lattice should be above the garden bed. I will be planting indeterminate varieties that, hopefully will all grow to a similar height.