Although some people can have success with a shorter tool it's my practice to make suggestions that will work for the population at large. The fact that the OP was not able to tighten properly the 1st time with the wrench at hand calls for a change in approach. Of course if one does not use good technique for tightening the pedals, such as pointing the crank toward the back and the wrench forward, it will make proper tightening more difficult even with the correct tool.