With the simplest of tools (some string, a tape measure and a heavy stick of wood), it is not difficult to understand the theory and the practice of setting your own drop spacing, and ensuring the stays are centered to the frame's center line. Have a look at How To String A Frame, before you head to the shop. Your confidence level might take a wee jump. That said...



Go slowly. Don't over bend, if you can avoid doing so. Measure several times, before each bend attempt - then bend...



It does not hurt to put a cloth cushion between the two by four and the frame. Think before you do and you will, likely, do just fine.

Hope this is helpful in elevating understanding, if not confidence.