Any question answered...

I would go with what shimano say's, as they tend to be very good at making things that are not compatible with their other things.

I use 7900 levers with another manufacturors brakes and they're fine, that said.

This way round is usually fine and less noticeable, but you would probably get better performance with the 'correct' matching brakes.

... and other responses above....

Some say "yes", some say "no" and some say "maybe". If I did decide to go with some matched levers, what can I get which are not STi levers. All the ones they have listed are STi, and I have already installed downtube shifters, so I am only looking for brake levers. What has got the same pull?

Non-Shimano would be fine.