Greetings -- Saw the thread about roof racks below and it got me thinking. I purchased a full-sized truck w/fiberglass topper this winter, and really hard to fork out $325 for a set of rails and 2, 1" square cross bars. Thinking about making 2 sets of wooded risers (2"-3") and wooden cross bars. Couple of questions: (1) If I bolt them thru the roof of the topper, what tink of backing plate do I need on the inside? and what should I use to get a water-tight seal? (2) What type of wood? I was thinking ash, but am open to suggestions. (3) How would I rail system within the cross bars to mount kayak and canoe cradles? Thanks in advance for your help. -- Greg