Thats too inflexible. If I'm putting together a complicated scene I like to resize manually on the fly. The visual scaling tool becomes useless if you can no longer harmonize dimensions because of it.Just make one the height you want and then duplicate it...
How about the snap to vertex. move your second object in the y direction, hold down the "V" and mmb over the vertex you want to size to, and you will then "snap" to that exact size.You could use create locator as a measuring tool, then put them in a layer so as not to select them...........dave