I put the carpet shampoo/vacs on the perimeter of the entrance and exit keeping the entrance to the bays open.
The site is not the best, unusual lot size. So I didn't want to block the bays with people vacuuming.
I had to build the bays at an angle to fit the wash (5+1). The customers actually like it especially those towing boats.
My vac income is down (about 15%) compared to my other wash vacs that are in front of the bays (I built them in 1978 & 1980).
I bought 6 carpet/vac machines with bonus time. Not so sure it was the right decision though. Wished I bought 2-3 car./vacs and 2-3 mega vacs instead.
I have 1 mega vac at another wash and it does a lot better than my regular vacs.
But saying all that I believe that unless your in a very small market eventually a competitor will open up with
credit card acceptors. I just think it's better to be the first with cc before anyone else.