Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
The mainsail leech is about 26.5'. So, a non-adjustable topping lift would need to be slightly longer to accomodate the extra run to the end of the boom and to allow the topping lift to slack off when the main is hoisted.
Here's the link to the manuals and specifications page, but I couldn't find any reference to the topping lift. However, I would recommend an adjustable topping lift, either halyard type or block-and-tackle type, in which case the exact measurement is not necessary.
Then, there's the question of whether you want to cleat it off forward on the boom, or run it all the way to the cockpit. For a simple rig, I suggest a cleat where you can reach it from the companionway step. For fancier rigs, use the Search feature to look at previous threads.
Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.