Number of trusses?

In practice neither do I but the gh roof does.  Just wondered whether there was a school of thought.

I do the same JJB I don't like them to grow to close to the ridge because that's were the cucs grow across a wire.

I agree.  In a reasonably small space, the cucs grow up to and alongside  the ridge line so the toms haven't got the choice of using the 'attic' they have to be pinched out a couple of inches after they hit glass. I can't even reach the ridge in new GH so toms may get a bit more headroom.  Half my problem is growing too much in one space.  Each year I vow not to, then make the same choices as always.  Some people never learn!    I begin to see the problem when in late summer I'm having to bend double just to get in past the greenery!