Interchangeable
Yes, all our tops and bottoms can be mixed and that is why we also sell them separately, if you got a new 4.2 sail and you need a shorter mast, all you need is a 370 top or if you are getting a new 5.3 sail just get the 430 bottom.
For the chart: Starting from a full mast (Example: 400 Top/Bottom) if you need to go smaller just get the 370 top and if you need to go bigger get the 430 bottom.
By doing this you are allowing the mast to remain close to top flex which keeps your draft lower and forward.
Consistency
Goya masts have the smoothest and most consistent built in the industry, made possible through higher pressure and better materials. There is not even 1mm of difference on the bend between our masts.
http://goyawindsurfing.com/masts/y2012/