Not only do the roll bars have to be structural components of the car the drivers and passenger helmets must be below the top of the bars. we have found that unless you are extremely short your helmet would not be below the bar.
I know that we do not have any instructors that would be able to qualify.
  Unfortunately this is the situation with the honda and dodge viper and others.

Im borrowing my friends S2000 as well for the driver training. It also doesnt have a roll bar but it does have a Mugen hardtop. Does this qualify? As far as I can remember I remember the miata guys need a hardtop for trackdays if they dont have a bar so I dont see the S2K being any different.
Also my buddy is going to order a set of track R comps with rims but probably wont be here till after the driver training... Can I run with 3 month old Bridgestone Blizzaks snow tyres??? I realize the grip level will be alot lower but it makes it more predictable and would exagerate the dynamics of the car (just like how skippy or jim russel run street tyres instead of full slicks on open wheel school cars)

Hey, we have a stock seat & seat belt you can bolt in
your Miata for driver training instead of the S2000.
Just an Idea. You can come pick one up or even get Tom to install it for you.