Comfort is another factor. If it's not comfortable then something is wrong. The bridge should also allow free movement of the cue. Keep it loose enough that the cue slides easily back and forth. If you bridge too tight, you'll be fighting your stroke.
Some players say to use only an open hand bridge, others a closed hand.
I say use a mixture. Shots made with a lot of speed might be better off with a closed hand bridge, while shots where you're bridging close to the cue ball might be better off with an open hand bridge. Use what's comfortable. Experiment around a bit and see how many bridges you can make. Make a game out of it.