Join Date: Feb 2000
Location: Annapolis, Md
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I have sailed traditional boats with and without roach in their sails. It really does make a huge difference to how the boat sails, in many ways a greater difference on a traditional boat than on a more modern boat. The difference is often being able to sail and make progress in lighter winds when traditional boats are at their most challenged converting non-sailing day's to sailing days. The difference is often a flatter sail shape in a blow and so delays the need to reef and the amount of heel.
Beyond that I am not sure that the amount of roach is relevant to your topping lift concern. Almost all coastal cruising sails built since the 1950's have been built with some roach, and no matter what you do, if you have battens, some roach (no matter how small) and a topping lift, there will be some interaction. The only way to avoid that interaction would be to go to a hollow leech and that would be absolutely crazy, far more blasphemous than the larger roach being suggested by your sailmaker.
I don't know what the story is with TrueBlue's boat, but I sail on boats with huge amounts, far more roach than your sailmaker is probably suggesting. Frankly, the interation between the topping lift and the backstay is just not a problem. They are typically set up just the way that you are describing where the hoist of the sail lifts the clew end of the boom and slacks the topping lift. (You may see how that works in the photo that is my avatar.)
Keep the roach, you'll really like it.