Posted: 11/05/2016 at 14:31
That;s the size of trough that I use - three plants per trough. I've done it for years, and get more tomatoes that I can eat fresh - but they make wonderful passata or chutney!.
The difficulty may be in supporting them. I have found that three canes per trough about 4ft high, linked at the top with square-lashed cross pieces (and the top canes link each of the troughs, too) together with short angled braces at the bottom, is more than adequate.
I have a picture somewhere to show what I mean - if I can find it, and then work out how to post it!