Bronstein rules state that increments don't stack: this has more of the flavour of traditional byo-yomi in Go: an increment can never increase your total time beyond where it was at the start of your move.
I think this would make an excellent rapid control for Go servers, incidentally: say 3 minutes main time with a Bronstein increment of 10s. I'd certainly prefer it to the Canadian-type "twenty-five moves in four minutes" settings - it would keep the pace of the game more even.