: I intend to build a Cirrus hybrid. I already have the s&g plans. This year I
: built a CLC Ch17 and the construction was fairly simple. The plans for the
: Cirrus call for a strongback to be built. I am wondering if this is
: necessary. My Ch17 is very accurate and tracks like a train using saw
: stools and winding sticks. Any opinions on the need for a storgback?

internal forms on a strong back are to give a shape to the hull that could not occur without them. Tracking characteristics have very little to do with the manner of construction. If you look at the entry/exit lines of your Ch17 the panels come together into a very fine edge like a tapered prism with near vertical sides. That is dictated to a large extent by the restricted bend possible with sheerclamp. While very fine ends may sound like a nice thing it does have some problems as there isn't much developing volume above that fine entry which makes for ends that stick in waves. It's not that much of a problem in the stern but in the bow it can affect handling a lot. Using some kind of forms or simply building with 4mm WITHOUT pre-glued sheerclamps can enable the hull shape to develop in such a way that the bow can "cork up" when approaching waves, which is a characteristic the Chesapeakes lack. Some of that is the relatively low rocker but most of it is that there isn't much deadrise/flare up near the bow.
The Chesapeake construction technique is derived from the Yare/Severn where the hull was developed from two pieces of ply forced together. In the later 4,8 panel hulls there's a stiff side panel being brought together into one curve. You can make a hull that way but that doesn't mean you can get an optimal shape for paddling that way.