I can't say that I agree with hobnails about grubbing up tomatoes. I always let my tomatoes grow to four or five trusses and never have any problems with lower yields on the higher trusses. It all depends upon the varieties. I tend to grow a mixture of varieties and they require different treatment.
Last year, I alternated the plants, stopping every other plant at 4/5 trusses at the eaves of the greenhouse and letting the others grow up to the roof with 6/7 trusses.
This worked well with the cherry tomatoes where the higher trusses had lots of fruit and when I cut the foliage back later in the season they ripened well but I had difficulty in supporting some of the beefsteak varieties (mind you a truss of six fruits at 1.5lb per fruit is a large thing to manage anyway.
The polytunnel is more difficult as it is quite hard to put up supports for the fruits.
This year I am going to try "laying down" the plants. I have a small hydroponics kit growing two plants and I'm going to let them keep growing and lower the plants towards the ground as they reach the top of the greenhouse.
Its all experiments and what suits you.
That's very interesting HeadG. I knew about layering the bottom section, but not the top!
Let us know how you get on eh?
One thing I've noticed this year, is that the stems of ours, all Alicante, have been incredibly thick - even woody, and very sturdy. It's the first time I've given them more liquid manure feed than ever before, and I'm wondering if that's the difference.
The trusses are pretty hopeful, but seem to be slowing at about 4 or 5, which doesn't bother me, as we have about 50 odd plants all over the place, like in the greenhouse etc.