I was hoping that would not be true, but you are correct, that just might be a problem. I want to use Computers for the rental gear, but I also want to keep it simple.
Do you think a better idea would be a simple SPG, and then a computer in a boot with it? I know that in a sense even non air integrated computers are confusing, but those sorts of customers (the kind who find a even a non integrated computer confusing) maybe never check their depth gauges anyway.
One of the reasons I was thinking of an Air-Integrated design in the first place is that the customers would alternate between metric and imperial, and (presumably) the computer would let me swap back and forth as needed. If I go with a SPG and separate computer, I'll have to swap the SPG's back and forth physically. I guess there is no way around that.
Unless someone knows of a universally marked SPG that I do not know about. But that too might be confusing, too.
The other question is whether customers would like the PC printout of their dive. I am trying to shoot for a fairly high level of service to encourage repeaters, but I have no idea if the printout is something people would find appealing.