Two problems. First and foremost total touchless - inbay or tunnel is only able of getting 60-70% really clean and another 10-15% kind of clean and even those percentage fluctuate downward depending if you have dry arid condiitons or winter weather where roadsalt is present (cleaner) and extended periods of wet weather when very stubborn roadfilm (oil) is present (less clean).
Secondly, when people go to a tunnel car wash, they expect a great deal more than they do from any in-bay automatic. I have it explained to me this by numerous customers over the years when asked why they use in-bay automatics. Their reply is "They (in-bays) help me keep my car clean, then when I want or need a really good wash, I come to your car wash."
Your building is longer, you have more equipment, yet you still will be able to only get cars as clean as an in-bay automatic, you'll just be able to put out the same less than quality car wash a lot faster.
I've made and sold touchess equipment for years. When we have told people that their cost per car just for pre-soak will be between 40-60 cents per car, they have all sat there and said, " That's ok, as long as we get good cars." All of sudden, that 10,000 cars they washed last month cost them 5,000 just for pre-soak. Then the game I like to call "Name That Tune" begins. They start lowering the concentration trying to get more cars per drum of chemical. Well, what happens? I'll tell you, instead of getting 85-90% of vehicles clean, that falls to 50-60% or less. No car wash can survive at that level of customer satisfaction.