Over-watering toms is an interesting point...
Our very best Shirley last year, by a country-mile, were the half a dozen plants I literally chucked into a spare area of soil, all scrunched up next to the runner beans, and they just romped away!
I always grow Shirley in the GH, and also in various locations around the house, all in pots and trays, and they are the staple tom here! We try and remember to pick them before we water/feed them!
I was going to try and do just one plant per 10" pot this year, but have bought far too many seeds, (first lot took ages to germinate, and I thought I'd lost them, then they all came through a couple of seconds after I'd rushed out and bought some more seed, which are now well on their way...), so I'll do what I normally do, plant two per pot and increase the yield everywhere!
I'm also trying a new one for me, Orkado, but only have seven plants at the moment! The rest of them are Roma from a free packet I was given last year on the instructions that a chum could have the plants, as she can never seem to get them away..:0~