The size, thickness, placement and material of the bridge plate effects the overall tone of an acoustic guitar more then some builders would like to admit. Building a bridge plate too large has a negative effect on a guitar. Placement of the bridge plate is more for construction purposes then personal.
Balance is the key word here.
Don't have a lot more bridge plate wood infront of the bridge then behind it, and versa visa. Try and balance out the bridge plates dimensions to correlate with the bridge placement. Bridge plate materials used in modern acoustic guitars are usually maple or e.i. rosewood. Both are excellent woods and work very well. Sometimes rosewood has a lot of resin and oils in it and can make gluing very difficult.