Creister, first I'm definitely not an authority out here just sharing what works for me. I think you'll get conflicting info on that idea (which is fine) but the only thing I can say is that I space 5' between each in a row and 6' between rows and I plant two plants in each hole which works for me. Could I plant one plant every 2.5 feet and get the same result??? probably so, but I don't have that many tomato cages
In your scenario where you only have about 2' between double planting may be too thick...