Renko Back Testing Open Prices Only - Reliable?

[gangsta1]

I have read lots of information stating that back testing on generated offline renko charts is unreliable, however looking at the visual back tests it seems as though the tests are reliable when the EA does not use a fixed stop loss or take profit but rather opens and closes trades based on open prices. Does anyone know if back testing renko with open prices only (using an EA that enter/exits based on open prices) are reliable? If not, why not? I was under the impression that the unreliability of back testing renko was due to the fact that price action could go a number of pips above/below a renko bar and not close in the opposite direction or trigger a stop loss if this movement was not enough to create a new bar in that direction hence if the criteria was only to use open prices then this would not be an issue. Maybe I am missing something but thought I would check in case I waste more time testing on renko charts.